Fix gcc build error while CONFIG_REGULATOR is not set

drivers/power/supply/ucs1002_power.o: In function `ucs1002_probe':
drivers/power/supply/ucs1002_power.c:593: undefined reference to `devm_regulator_register'
drivers/power/supply/ucs1002_power.o:(.rodata+0x3b8): undefined reference to `regulator_enable_regmap'
drivers/power/supply/ucs1002_power.o:(.rodata+0x3c0): undefined reference to `regulator_disable_regmap'
drivers/power/supply/ucs1002_power.o:(.rodata+0x3c8): undefined reference to `regulator_is_enabled_regmap'

Add Kconfig dependency to CONFIG_REGULATOR.
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 9a2688e4 ("power: supply: Add driver for Microchip UCS1002")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>