regulator: mt6311: MT6311_REGULATOR needs to select REGMAP_I2C

This patch fix the below build error:
drivers/regulator/mt6311-regulator.c:111: undefined reference to `__devm_regmap_init_i2c'
Signed-off-by: Henry Chen <henryc.chen@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

drivers/regulator/Kconfig

@@ -446,6 +446,7 @@ config REGULATOR_MC13892
 config REGULATOR_MT6311
 	tristate "MediaTek MT6311 PMIC"
 	depends on I2C
+	select REGMAP_I2C
 	help
 	  Say y here to select this option to enable the power regulator of
 	  MediaTek MT6311 PMIC.