arm: MediaTek: add basic support for MT7629 boards

This adds a general board file based on MT7629 SoCs from MediaTek.

Apart from the generic parts (cpu) we add some low level init codes
and initialize the early clocks.

Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index f5d4d39..96eadb6 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -664,6 +664,20 @@
 	  targeted at media players and tablet computers. We currently
 	  support the S905 (GXBaby) 64-bit SoC.
 
+config ARCH_MEDIATEK
+	bool "MediaTek SoCs"
+	select BINMAN
+	select DM
+	select OF_CONTROL
+	select SPL_DM if SPL
+	select SPL_LIBCOMMON_SUPPORT if SPL
+	select SPL_LIBGENERIC_SUPPORT if SPL
+	select SPL_OF_CONTROL if SPL
+	select SUPPORT_SPL
+	help
+	  Support for the MediaTek SoCs family developed by MediaTek Inc.
+	  Please refer to doc/README.mediatek for more information.
+
 config ARCH_LPC32XX
 	bool "NXP LPC32xx platform"
 	select CPU_ARM926EJS
@@ -1449,6 +1463,8 @@
 
 source "arch/arm/mach-meson/Kconfig"
 
+source "arch/arm/mach-mediatek/Kconfig"
+
 source "arch/arm/mach-qemu/Kconfig"
 
 source "arch/arm/mach-rockchip/Kconfig"