power: regulator: max77686 correct variable type

The return type of pmic_read and pmic_write is signed int, so
correct variable 'ret' from type unsigned int to int.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Przemyslaw Marczak <p.marczak@samsung.com>
1 file changed