ASoC: apq8084: add NULL pointer check for function return value

Add check for NULL pointer as return value from function before
dereferencing the pointer.

CRs-Fixed: 682545
Change-Id: I856f29e1f4a608e4de765a6b43214a55c896ef2f
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>