sunxi: Add SUN6I_P2WI kconfig entry

Add simple and meaningful kconfig option for p2wi.c
instead of using MACH type on Makefile.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
diff --git a/arch/arm/mach-sunxi/Makefile b/arch/arm/mach-sunxi/Makefile
index 9713fd5..1284b0e 100644
--- a/arch/arm/mach-sunxi/Makefile
+++ b/arch/arm/mach-sunxi/Makefile
@@ -16,10 +16,10 @@
 ifndef CONFIG_MACH_SUN9I
 obj-y	+= usb_phy.o
 endif
+obj-$(CONFIG_SUN6I_P2WI)	+= p2wi.o
 obj-$(CONFIG_SUN6I_PRCM)	+= prcm.o
 obj-$(CONFIG_MACH_SUN8I)	+= prcm.o
 obj-$(CONFIG_MACH_SUN9I)	+= prcm.o
-obj-$(CONFIG_MACH_SUN6I)	+= p2wi.o
 obj-$(CONFIG_MACH_SUN8I)	+= rsb.o
 obj-$(CONFIG_MACH_SUN9I)	+= rsb.o
 obj-$(CONFIG_MACH_SUN4I)	+= clock_sun4i.o