regmap: reject volatile update_bits() in cache-only mode

regmap: reject volatile update_bits() in cache-only mode

Prevent _regmap_update_bits() from accessing hardware when the register
map is in cache-only mode.

Unlike regmap_raw_read() and _regmap_read(), the volatile
_regmap_update_bits() fast path bypasses the cache_only check. This can
result in unexpected hardware accesses while the device is suspended.

Return -EBUSY to ensure behavior is consistent with other cache-only
access paths.

Signed-off-by: bui duc phuc <phucduc.bui@gmail.com>
Link: https://patch.msgid.link/20260528053204.46783-1-phucduc.bui@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>