ASoC: rt1015: save boost_mode only if valid

Saves boost_mode only if valid.  Also returns -EINVAL if it is invalid.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20201224100607.3006171-3-tzungbi@google.com


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