regulator: fan53555: fill set_suspend_enable/disable callback

Setting the set_suspend_enable/disable callback to support
enable and disable the dcdc when system is suspend.

Signed-off-by: zhangqing <zhangqing@rock-chips.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>