regmap: Don't warn about cache only mode for devices with no cache

regmap: Don't warn about cache only mode for devices with no cache

For devices with no cache it can make sense to use cache only mode as a
mechanism for trapping writes to hardware which is inaccessible but since
no cache is equivalent to cache bypass we force such devices into bypass
mode. This means that our check that bypass and cache only mode aren't both
enabled simultanously is less sensible for devices without a cache so relax
it.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220622171723.1235749-1-broonie@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>