ASoC: msm8x16: avoid access of invalid memory

If ioremap fails, the current code goes ahead and
tries to access that remapped address causing a crash.
Return immediately upon ioremap failure.

CRs-Fixed: 747347
Change-Id: I0794e0cea56daa220438a7863125d0bca2be66c2
Signed-off-by: Aravind Kumar <akumark@codeaurora.org>