regulator: da9121: Return REGULATOR_MODE_INVALID for invalid mode

-EINVAL is not a valid return value for .of_map_mode, return
REGULATOR_MODE_INVALID instead.

Fixes: 65ac9704 ("regulator: da9121: add mode support")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Adam Ward <Adam.Ward.opensource@diasemi.com>
Link: https://lore.kernel.org/r/20210517052721.1063375-1-axel.lin@ingics.com


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