regulator: rt4831: Add bypass mask to fix set_bypass API work

To use set/get_bypass helper function, bypass mask need to be specified.

Signed-off-by: ChiYuan Huang <cy_huang@richtek.com>
Link: https://lore.kernel.org/r/1648171577-9663-2-git-send-email-u0084500@gmail.com


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