regmap: replace regmap_write_bits()

commit 23b92e4cf5fd ("regmap: remove regmap_write_bits()")
removed regmap_write_bits(), but MFD driver was using it.
So, commit e30fccd6771d ("regmap: Keep regmap_write_bits()")
turns out it, but it is using original style.
This patch uses regmap_update_bits_base() for regmap_write_bits()

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>