qdsp5: audio: Protect common data between ADSP ISR and flush operation

During NEEDS_DATA or BUFFER_UPDATE event processing in ISR
context, if flush command is issued by application then
there is chance of concurrent access of some of the variables
shared between ISR and Process context. This may result in race
condition causing values of these shared variables to be
inconsistent.

Fix this by protecting these variables using spin lock. Also corrected
locking sequence order in encode drivers.

Change-Id: I06b4d08053ad13d1b118ab6f29e69e95b49d133f
Signed-off-by: Manish Dewangan <manish@codeaurora.org>