firmware: cs_dsp: Add lockdep asserts to interface functions

Some of the control functions exposed by the cs_dsp code require the
pwr_lock to be held by the caller. Add lockdep_assert_held calls to
ensure this is done correctly.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20211117132300.1290-2-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>