sunxi: Add SUN8I_RSB kconfig entry

Add simple and meaningful kconfig option for rsb.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 87b0c57..64407db 100644
--- a/arch/arm/mach-sunxi/Makefile
+++ b/arch/arm/mach-sunxi/Makefile
@@ -18,8 +18,7 @@
 endif
 obj-$(CONFIG_SUN6I_P2WI)	+= p2wi.o
 obj-$(CONFIG_SUN6I_PRCM)	+= prcm.o
-obj-$(CONFIG_MACH_SUN8I)	+= rsb.o
-obj-$(CONFIG_MACH_SUN9I)	+= rsb.o
+obj-$(CONFIG_SUN8I_RSB)		+= rsb.o
 obj-$(CONFIG_MACH_SUN4I)	+= clock_sun4i.o
 obj-$(CONFIG_MACH_SUN5I)	+= clock_sun4i.o
 obj-$(CONFIG_MACH_SUN6I)	+= clock_sun6i.o