regmap: cache: Return error in cache sync operations for REGCACHE_NONE

regmap: cache: Return error in cache sync operations for REGCACHE_NONE

[ Upstream commit fd883d79e4dcd2417c2b80756f22a2ff03b0f6e0 ]

There is no sense in doing a cache sync on REGCACHE_NONE regmaps.
Instead of panicking the kernel due to missing cache_ops, return an error
to client driver.

Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Link: https://lore.kernel.org/r/20230313071812.13577-1-alexander.stein@ew.tq-group.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>