usb: gadget: Fix synchronization issue between f_audio_source

Race is happening when both audio_pcm_close() and audio_send()
executes in parallel.
When the PCM session is closed, the substream attribute of the
audio_dev structure is set to NULL in audio_pcm_close().
As there is no synchronization protection for the audio_dev subtream
attributes in audio_send(), it is causing NULL pointer dereference.
Hence fixing the issue by adding proper synchronization protection
for the audio_dev subtream attributes in audio_send().

CRs-Fixed: 613498
Change-Id: Id9ab0d4e347b8bb2f551f9033829e541bdcaf0e8
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>
msm: socinfo: Introduce soc string

OEMs require the soc-id to be translated to a string
by the kernel and reported as a part of machine init
routines. Add support for it

Change-Id: I1ebdcd21061bde60815090a2d7de475a4e235f0a
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>
ARM: Introduce arch_read_hardware_id