ASoC: wcd9330: Avoid NULL pointer access

It is possible that codec private data will
be accessed without creating memory when
sound card is not registered. Avoid kernel
crash by checking it for NULL and return without
access.

CRs-Fixed: 657811
Change-Id: I4d8636252d2b75aa964eaf0c1b3d44e3f0976771
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>