ARM: MediaTek: Add support for MediaTek MT7622 SoC

Add support for MediaTek MT7622 SoC. This include the file
that will initialize the SoC after boot and its device tree.

diff --git a/arch/arm/mach-mediatek/Makefile b/arch/arm/mach-mediatek/Makefile
index 6129ac8..290d2c7 100644
--- a/arch/arm/mach-mediatek/Makefile
+++ b/arch/arm/mach-mediatek/Makefile
@@ -4,6 +4,7 @@
 obj-$(CONFIG_SPL_BUILD)	+= spl.o
 
 obj-$(CONFIG_MT8512) += mt8512/
+obj-$(CONFIG_TARGET_MT7622) += mt7622/
 obj-$(CONFIG_TARGET_MT7623) += mt7623/
 obj-$(CONFIG_TARGET_MT7629) += mt7629/
 obj-$(CONFIG_TARGET_MT8516) += mt8516/