arm64: select PINCTRL for ZTE platform

Select PINCTRL for ZTE platform, so that we can have ZX pinctrl driver
options available for enabling.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm64/Kconfig.platforms

@@ -250,6 +250,7 @@ config ARCH_XGENE
 
 config ARCH_ZX
 	bool "ZTE ZX SoC Family"
+	select PINCTRL
 	help
 	  This enables support for ZTE ZX SoC Family