msm: qdsp5: Protect avsync mask access with spin lock to make it SMP safe

avsync mask gets accessed in both process and Adsp ISR context. local
irq is disabled while accessing this variable on process context,
this ensures that avsync doesn't get accessed concurrently in
Adsp ISR context. But this holds true only for uniprocessor
environment, On multi-processor Adsp ISR may come on other core
which may result in inconsistent value of avsync mask.

Fix this by protecting avsync mask with spin lock.

Change-Id: I711b152b512502484c2382be633b3887c9600334
Signed-off-by: Manish Dewangan <manish@codeaurora.org>