regulator: mt6315: Fix off-by-one for .n_voltages

The valid selector is 0 ~ 0xbf, so the .n_voltages should be 0xc0.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Link: https://lore.kernel.org/r/20210311020558.579597-1-axel.lin@ingics.com


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