regmap: Move the handling for max_raw_write into regmap_raw_write

Currently regmap_bulk_write will split a write into chunks before
calling regmap_raw_write if max_raw_write is set. It is more logical
for this handling to be inside regmap_raw_write itself, as this
removes the need to keep re-implementing the chunking code, which
would be the same for all users of regmap_raw_write.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>