regulator: tps65910: fix a missing check of return value

[ Upstream commit cd07e3701fa6a4c68f8493ee1d12caa18d46ec6a ]

tps65910_reg_set_bits() may fail. The fix checks if it fails, and if so,
returns with its error code.

Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>