We need hold lock each time updating shirm registers, otherwise,
we may set unexpected values to them when they are set in
different thread at different time sequence.

The notification work will be scheduled in global work queue,
which won't hold this sst->spinlock itself, so here we need
change to use the lock version to update shim registers.
Signed-off-by: Jie Yang <yang.jie@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>