qcom-fm: audio: add support for FM feature

-Add set_fm_volume() to set handle fm volume

Change-Id: I2a2c6a60b9855d9360ff8fb90849517e77e5faab

Conflicts:

	audio/AudioPolicyManagerBase.cpp
	include/hardware_legacy/AudioSystemLegacy.h
Merge commit 'refs/changes/97/33297/1' of http://review.cyanogenmod.org/CyanogenMod/android_hardware_libhardware_legacy into cm-10.1