mips: add base support for QCA/Atheros ath79 SOCs

This patch add some common code for QCA/Atheros ath79 SOCs such as
DDR tuning, chip reset and CPU detection.

Signed-off-by: Wills Wang <wills.wang@live.com>
diff --git a/arch/mips/mach-ath79/Kconfig b/arch/mips/mach-ath79/Kconfig
new file mode 100644
index 0000000..7d8ce09
--- /dev/null
+++ b/arch/mips/mach-ath79/Kconfig
@@ -0,0 +1,7 @@
+menu "QCA/Atheros 7xxx/9xxx platforms"
+	depends on ARCH_ATH79
+
+config SYS_SOC
+	default "ath79"
+
+endmenu