radio-iris: Configure repeat count for PS string

- When FM Rx tuned to a station, not receiving complete PS string.
  SOC is not waiting for complete PS string. it is sending PS event
  even if it has part of PS string as well.
- Added support for setting repeat count for PS string
  to get refined PS string from receiver.

CRs-Fixed: 474719
Change-Id: I71c0c1c8af9488573c05d816c37982f9ed935a87
Signed-off-by: Venkateshwarlu Domakonda <Venkateshwarlu@codeaurora.org>
radio: iris: Add the parameter to turn on/off sig blend

FM driver will always enable the sig blend feature, it will cause
FM seperation failure during lab test.So add this new parameter
to disable the feature by adb command to pass the test.

Change-Id: I187d4e5fff4aabfb994a905e174bb8ce941e2c16
Signed-off-by: Sheng Fang <fsheng@codeaurora.org>
radio: iris: Add NULL pointer check

Dereferencing a NULL pointer may cause kernel crash,
Check for NULL pointer before dereferencing

Conflicts:
        drivers/media/radio/radio-iris.c

Change-Id: Ic3368d619d23c76702d95e0f69e41394e423a296
CRs-Fixed: 548404
Signed-off-by: Ayaz Ahmad <aahmad@codeaurora.org>