DT: MIPS: ralink: add RT3883 dts files

Add a dtsi file for RT3883 SoC and a sample dts file.

Signed-off-by: John Crispin <blogic@openwrt.org>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Patchwork: http://patchwork.linux-mips.org/patch/5189/
diff --git a/arch/mips/ralink/Kconfig b/arch/mips/ralink/Kconfig
index 2f6fbb8..493411f 100644
--- a/arch/mips/ralink/Kconfig
+++ b/arch/mips/ralink/Kconfig
@@ -42,6 +42,10 @@
 		bool "RT305x eval kit"
 		depends on SOC_RT305X
 
+	config DTB_RT3883_EVAL
+		bool "RT3883 eval kit"
+		depends on SOC_RT3883
+
 endchoice
 
 endif