sunxi: add DRAM_SUN6I kconfig

Add proper and simple kconfig option for dram_sun6i.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/Kconfig b/arch/arm/mach-sunxi/Kconfig
index 1a179e1..360a9ca 100644
--- a/arch/arm/mach-sunxi/Kconfig
+++ b/arch/arm/mach-sunxi/Kconfig
@@ -6,6 +6,12 @@
 config IDENT_STRING
 	default " Allwinner Technology"
 
+config DRAM_SUN6I
+	bool
+	help
+	  Select this dram controller driver for Sun6i platforms,
+	  like A31/A31s.
+
 config SUN6I_P2WI
 	bool "Allwinner sun6i internal P2WI controller"
 	help
@@ -119,6 +125,7 @@
 	select CPU_V7_HAS_NONSEC
 	select CPU_V7_HAS_VIRT
 	select ARCH_SUPPORT_PSCI
+	select DRAM_SUN6I
 	select SUN6I_P2WI
 	select SUN6I_PRCM
 	select SUNXI_GEN_SUN6I