hal: Add changes for dolby DS2

-Add device to back end mapping for APQ8084 and MSM8994.
-Set initialization info like sound card number, dmid
 to ds2 dap hal.
-Add mixer control DS2 OnOff to enable or disable DS2
-A property "audio.dolby.ds2.enabled" is added to trigger
 the mixer control.
-Reuse ds1 functions for checking dolby format and getting
 sound codec id.

CRs-Fixed: 661095 661018

Conflicts:
	hal/audio_hw.c
        hal/msm8916/platform.c

Change-Id: Iff5fdc49249eb035c2ccde18e190ccc6c3ff632a