[rilmodem] Add initial SIM ATK support

Add initial SIM ATK implementation to rilmodem driver, supporting
proactive command, terminal response and envelope.

Signed-off-by: Petri Takalokastari <petri.takalokastari@oss.tieto.com>

[rilmodem] Fix proactive command and terminal response handling

Convert the proactive commands and terminal responses to correct
format

[rilmodem] Fix for envelope sending

Fix typo in envelope sending causing ofono crash

[rilmodem] stk: adjust timings

Adjust the registeration of the rilmodem stk service and usage of timer
when reporting to RIL when ready to receive proactive commands

[rilmodem] Fix for terminal response and envelope construction

Remove usage of strlen, so the terminal responses and envelopes ending
with value 0x00 are sent properly.

[rilmodem] Remove timer usage from start up sequence

Remove usage of timers in startup sequence. Report ofono readiness to
receive proactive commands only when agent has registered.

[rilmodem] Fine tuning of start up sequence

Register to listen STK specific unsolicited messages only if UI STK agent
has registered. This because RILD will send and buffer proactive commands
also if not received RIL_REQUEST_REPORT_STK_SERVICE_IS_RUNNING
previously. RILD will buffer the proactive command until receiving
RIL_REQUEST_REPORT_STK_SERVICE_IS_RUNNING or terminal
response to (sent) proactive command.
By this change oFono core/rilmodem will not handle proactive commands
until STK UI agent has been registered to oFono.

[rilmodem] Change envelope sending request

Changed envelope sending request from
RIL_REQUEST_STK_SEND_ENVELOPE_WITH_STATUS to
RIL_REQUEST_STK_SEND_ENVELOPE_COMMAND as it seems that RILD
does not support RIL_REQUEST_STK_SEND_ENVELOPE_WITH_STATUS
properly.
Also cleaned up some excessive tracing.
Merge pull request #158 from ptakalok/stk

[rilmodem] Add initial SIM ATK support