regulator: hi655x: Remove ctrl_mask field from struct hi655x_regulator

The rdev->desc->enable_mask setting is always the same as
BIT(regulator->ctrl_mask), so just use rdev->desc->enable_mask instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>