ASoC: wcd9xxx: Add check for NULL pointer and buffer overflow

Current code has possible scenarios where NULL pointer
could be dereferenced or an out-of-bound index of array
could be accessed. The change checks the pointer for NULL
before they are dereferenced and checks for buffer overflows
to ensure out of bound indexes of arrays are not
accessed.

CRs-Fixed: 628865 628869 628873 628874 628875
Change-Id: I3002d1831eb852445619dabeb0f26285ab420953
Signed-off-by: Aravind Kumar <akumark@codeaurora.org>