broadband-modem-qmi: try to use Band Preference for current caps if available

The "NAS Get System Selection Preference" response may come without "Mode
Preference". If that is found, look for "Band Preference" and "LTE Band
Preference" TLVs and try to build capabilities from those.

This makes my UML290 properly report CDMA/EVDO+LTE capabilities:

ModemManager[16586]: [/dev/cdc-wdm0] Received message...
>>>>>> QMUX:
>>>>>>   length  = 55
>>>>>>   flags   = 0x80
>>>>>>   service = "nas"
>>>>>>   client  = 1
>>>>>> QMI:
>>>>>>   flags       = "response"
>>>>>>   transaction = 1
>>>>>>   tlv_length  = 43
>>>>>>   message     = "Get System Selection Preference" (0x0034)
>>>>>> TLV:
>>>>>>   type       = "Result" (0x02)
>>>>>>   length     = 4
>>>>>>   value      = 00:00:00:00
>>>>>>   translated = SUCCESS
>>>>>> TLV:
>>>>>>   type       = "Emergency mode" (0x10)
>>>>>>   length     = 1
>>>>>>   value      = 00
>>>>>>   translated = 0
>>>>>> TLV:
>>>>>>   type       = "Band Preference" (0x12)
>>>>>>   length     = 8
>>>>>>   value      = 07:00:00:00:00:00:00:00
>>>>>>   translated = 7
>>>>>> TLV:
>>>>>>   type       = "CDMA PRL Preference" (0x13)
>>>>>>   length     = 2
>>>>>>   value      = FF:3F
>>>>>>   translated = 16383
>>>>>> TLV:
>>>>>>   type       = "Roaming Preference" (0x14)
>>>>>>   length     = 2
>>>>>>   value      = FF:00
>>>>>>   translated = 255
>>>>>> TLV:
>>>>>>   type       = "LTE Band Preference" (0x15)
>>>>>>   length     = 8
>>>>>>   value      = 00:00:00:00:00:00:00:00
>>>>>>   translated = 0
ModemManager[16586]: KEY: 01:00:01:03:00:00:00:00
ModemManager[16586]:   Service: 03
ModemManager[16586]:   Client ID: 01
ModemManager[16586]:   Transaction ID: 01:00
ModemManager[16586]: <debug> [1347005734.979115] [mm-broadband-modem-qmi.c:321] load_current_capabilities_get_system_selection_preference_ready(): Mode preference not reported in system selection preference
ModemManager[16586]: <debug> [1347005734.979131] [mm-broadband-modem-qmi.c:333] load_current_capabilities_get_system_selection_preference_ready(): Valid bands reported in system selection preference: 'bc-0-a-system, bc-0-b-system, bc-1-all-blocks'
ModemManager[16586]: <debug> [1347005734.979141] [mm-broadband-modem-qmi.c:341] load_current_capabilities_get_system_selection_preference_ready(): LTE band preference found
ModemManager[16586]: [/dev/cdc-wdm0] Sending message...
<<<<<< QMUX:
<<<<<<   length  = 12
<<<<<<   flags   = 0x00
<<<<<<   service = "dms"
<<<<<<   client  = 1
<<<<<< QMI:
<<<<<<   flags       = "none"
<<<<<<   transaction = 1
<<<<<<   tlv_length  = 0
<<<<<<   message     = "Get Capabilities" (0x0020)
ModemManager[16586]: KEY: 01:00:01:02:00:00:00:00
ModemManager[16586]:   Service: 02
ModemManager[16586]:   Client ID: 01
ModemManager[16586]:   Transaction ID: 01:00
ModemManager[16586]: <debug> [1347005734.982676] [mm-at-serial-port.c:392] debug_log(): (ttyACM0): <-- '<CR><LF>OK<CR><LF>'
ModemManager[16586]: <debug> [1347005734.982751] [mm-serial-port.c:969] mm_serial_port_close(): (ttyACM0) device open count is 2 (close)
ModemManager[16586]: <debug> [1347005734.982797] [mm-at-serial-port.c:392] debug_log(): (ttyACM0): --> 'AT+CMEE=1<CR>'
ModemManager[16586]: [/dev/cdc-wdm0] Received message...
>>>>>> QMUX:
>>>>>>   length  = 38
>>>>>>   flags   = 0x80
>>>>>>   service = "dms"
>>>>>>   client  = 1
>>>>>> QMI:
>>>>>>   flags       = "response"
>>>>>>   transaction = 1
>>>>>>   tlv_length  = 26
>>>>>>   message     = "Get Capabilities" (0x0020)
>>>>>> TLV:
>>>>>>   type       = "Result" (0x02)
>>>>>>   length     = 4
>>>>>>   value      = 00:00:00:00
>>>>>>   translated = SUCCESS
>>>>>> TLV:
>>>>>>   type       = "Info" (0x01)
>>>>>>   length     = 16
>>>>>>   value      = B0:9D:57:00:00:DD:6D:00:03:02:05:01:02:04:05:08
>>>>>>   translated = [ max_tx_channel_rate = '5742000' max_rx_channel_rate = '7200000' data_service_capability = '3' sim_capability = '2' radio_interface_list = '{ [0] = '1 ' [1] = '2 ' [2] = '4 ' [3] = '5 ' [4] = '8 '}' ]
ModemManager[16586]: KEY: 01:00:01:02:00:00:00:00
ModemManager[16586]:   Service: 02
ModemManager[16586]:   Client ID: 01
ModemManager[16586]:   Transaction ID: 01:00
ModemManager[16586]: <debug> [1347005734.983353] [mm-broadband-modem-qmi.c:183] modem_load_current_capabilities_finish(): loaded current capabilities: cdma-evdo, lte
cli: include both current and modem capabilities in modem report