regulator: Modify ramp_delay value for s5m8767a

As s5m8767a is revisioned, ramp_delay register is changed.
5mV/uS, 10mV/uS, 25mV/uS, 50mV/uS, 100mV/uS ramp delay can be selected.

Signed-off-by: Sangbeom Kim <sbkim73@samsung.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>