Audio: sst: Prevents concurrent access to firmware download code

Audio: sst: Prevents concurrent access to firmware download code

BZ: 20940

OldBZ:9443

The code to download firmware can be accessed by more than one thread at a time
leading to panic. Proper locking along with a new sst state (firmware starting
to download) prevents this. (Ported to gb-stable)

Change-Id: Ic56e3bfd68cf89c2b8937a572a70f01b80e3b27e
Old-Change-Id: I16ef33e6ed26407ffe2e7c7693976ce1ec8e09cb
Signed-off-by: Omair Mohammed Abdullah <omair.m.abdullah@intel.com>
Reviewed-on: http://android.intel.com:8080/32721
Reviewed-by: M, Arulselvan <arulselvan.m@intel.com>
Tested-by: M, Arulselvan <arulselvan.m@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>