qdsp5: adsp: Add NULL check in adsp driver functions

ADSP driver functions are directly accessing module without checking
for NULL. This can result in crash if module supplied points to NULL.

Added NULL check to solve this.

Change-Id: I47eef0ea03086935ebfe33a2585ba214780e73f7
Signed-off-by: Manish Dewangan <manish@codeaurora.org>