regulator: uniphier: Fix build dependency

This driver does not use any syscon APIs, so remove MFD_SYSCON dependency.
Select REGMAP_MMIO since this driver uses devm_regmap_init_mmio().
Signed-off-by: NAxel Lin <axel.lin@ingics.com>
Signed-off-by: NMark Brown <broonie@kernel.org>

drivers/regulator/Kconfig

@@ -1011,7 +1011,8 @@ config REGULATOR_TWL4030
 config REGULATOR_UNIPHIER
 	tristate "UniPhier regulator driver"
 	depends on ARCH_UNIPHIER || COMPILE_TEST
-	depends on OF && MFD_SYSCON
+	depends on OF
+	select REGMAP_MMIO
 	default ARCH_UNIPHIER
 	help
 	  Support for regulators implemented on Socionext UniPhier SoCs.