regulator: lp8755: Get rid of lp8755_read/lp8755_write/lp8755_update_bits

Just use regmap_read/regmap_write/regmap_update_bits instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20200802090638.380589-1-axel.lin@ingics.com


Signed-off-by: Mark Brown <broonie@kernel.org>