Bluetooth: Parameters for outgoing SCO connections

In order to establish a transparent SCO connection, the correct settings must
be specified in the Setup Synchronous Connection request. For that,
voice_setting is added to ACL connection flags to set up the desired
parameters. If this value is zero, a legacy SCO connection will be requested.
This patch uses T2 settings.
Bluetooth: Fallback transparent SCO from T2 to T1

When initiating a transparent eSCO connection, make use of T2 settings at
first try. T2 is the recommended settings from HFP 1.6 WideBand Speech. Upon
connection failure, try T1 settings.
To know which of T2 or T1 should be used, conn->fallback is used.  Bluez only
attempt to reconnect twice, but still test conn->fallback as a preventive
measure.
T2 failure is detected if Synchronous Connection Complete event fails with
error 0x0d. This error code has been found experimentally by sending a T2
request to a T1 only SCO listener. It means "Connection Rejected due to
Limited resource".