arm: add basic support for Mediatek MT6589 boards

This adds a generic devicetree board file and a dtsi for boards
based on MT6589 SoCs from Mediatek.

Apart from the generic parts (gic, clocks) the only component
currently supported are the timers.

Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 6721fab..1895de2 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -172,6 +172,7 @@
 machine-$(CONFIG_ARCH_MV78XX0)		+= mv78xx0
 machine-$(CONFIG_ARCH_MVEBU)		+= mvebu
 machine-$(CONFIG_ARCH_MXC)		+= imx
+machine-$(CONFIG_ARCH_MEDIATEK)		+= mediatek
 machine-$(CONFIG_ARCH_MXS)		+= mxs
 machine-$(CONFIG_ARCH_NETX)		+= netx
 machine-$(CONFIG_ARCH_NOMADIK)		+= nomadik