ARM: MediaTek: Add support for MediaTek MT8512 SoC

Add support for MediaTek MT8512 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 b9b2355..6129ac8 100644
--- a/arch/arm/mach-mediatek/Makefile
+++ b/arch/arm/mach-mediatek/Makefile
@@ -3,6 +3,7 @@
 obj-y	+= cpu.o
 obj-$(CONFIG_SPL_BUILD)	+= spl.o
 
+obj-$(CONFIG_MT8512) += mt8512/
 obj-$(CONFIG_TARGET_MT7623) += mt7623/
 obj-$(CONFIG_TARGET_MT7629) += mt7629/
 obj-$(CONFIG_TARGET_MT8516) += mt8516/