ASoC: fsl: Fix lockups with recent cache changes

The recent series of changes to the caching in the SSI driver have
caused a number of problems to appear in some test systems.  These are
still not fully understood but we're coming up to the merge window so
for now let's revert commit 7de2763d

 (ASoC: fsl_ssi: Remove
.num_reg_defaults_raw from regmap_config) as backing that out seems to
resolve the problem on affected systems.

Reported-by: Maciej S. Szmigiero" <mail@maciej.szmigiero.name>
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Marek Vasut <marex@denx.de>