mfd: Fix val_len parameters for s5m-core regmap_raw_write

The val_len parameters for regmap_raw_write should be "count * sizeof(u8)"
(or simply "count") instead of "count * sizeof(u16)".

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>