mfd: Add s5m regulator operation mode

This patch add variables for opmode of s5m series.
S5M series have 4 operation modes.
Off mode is always regulator off mode.
On mode is always regulator on mode.
Lowpower mode is that regualtor operate in low-power.
Suspend mode is that regulator operation depends on AP suspend mode.

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