pinctrl: pistachio: Make it as an option

So it will be avilable for generic MIPS kernel.

--
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
v3: Depend on OF as well
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

drivers/pinctrl/Kconfig

@@ -248,12 +248,15 @@ config PINCTRL_SX150X
 	  - 16 bits: sx1509q, sx1506q
 
 config PINCTRL_PISTACHIO
-	def_bool y if MACH_PISTACHIO
+	bool "IMG Pistachio SoC pinctrl driver"
+	depends on OF && (MIPS || COMPILE_TEST)
 	depends on GPIOLIB
 	select PINMUX
 	select GENERIC_PINCONF
 	select GPIOLIB_IRQCHIP
 	select OF_GPIO
+    help
+	  This support pinctrl and gpio driver for IMG Pistachio SoC.
 
 config PINCTRL_ST
 	bool