mmc: check a return value about regulator's always-on

Regulator can be set to "always-on".
It's not error about enable/disable. It needs to check about
its condition.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
1 file changed