regmap: allow to define reg_update_bits for no bus configuration

[ Upstream commit 02d6fdec

 ]

Some device requires a special handling for reg_update_bits and can't use
the normal regmap read write logic. An example is when locking is
handled by the device and rmw operations requires to do atomic operations.
Allow to declare a dedicated function in regmap_config for
reg_update_bits in no bus configuration.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
Link: https://lore.kernel.org/r/20211104150040.1260-1-ansuelsmth@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Stable-dep-of: 3f42b142

 ("serial: max310x: fix IO data corruption in batched operations")
Signed-off-by: Sasha Levin <sashal@kernel.org>