arm: mach-k3: Move ARM64 specific code into new arm64 directory

Like we did with R5, move ARM64 code into a specific directory to make
it clear what code is only meant to run on each core type.

Signed-off-by: Andrew Davis <afd@ti.com>
diff --git a/arch/arm/mach-k3/Makefile b/arch/arm/mach-k3/Makefile
index 945698e..19b2d79 100644
--- a/arch/arm/mach-k3/Makefile
+++ b/arch/arm/mach-k3/Makefile
@@ -3,9 +3,8 @@
 # Copyright (C) 2017-2018 Texas Instruments Incorporated - https://www.ti.com/
 #	Lokesh Vutla <lokeshvutla@ti.com>
 
+obj-$(CONFIG_ARM64) += arm64/
 obj-$(CONFIG_CPU_V7R) += r5/
-obj-$(CONFIG_ARM64) += arm64-mmu.o
-obj-$(CONFIG_ARM64) += cache.o
 obj-$(CONFIG_OF_LIBFDT) += common_fdt.o
 ifeq ($(CONFIG_OF_LIBFDT)$(CONFIG_OF_SYSTEM_SETUP),yy)
 obj-$(CONFIG_SOC_K3_AM654) += am654_fdt.o