arm64: add arch/arm64/Kbuild

Use the standard obj-y form to specify the sub-directories under
arch/arm64/. No functional change intended.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/Kbuild

+# SPDX-License-Identifier: GPL-2.0-only
+obj-y			+= kernel/ mm/
+obj-$(CONFIG_NET)	+= net/
+obj-$(CONFIG_KVM)	+= kvm/
+obj-$(CONFIG_XEN)	+= xen/
+obj-$(CONFIG_CRYPTO)	+= crypto/

arch/arm64/Makefile

@@ -136,11 +136,7 @@ KASAN_SHADOW_OFFSET := $(shell printf "0x%08x00000000\n" $$(( \
 
 export	TEXT_OFFSET GZFLAGS
 
-core-y		+= arch/arm64/kernel/ arch/arm64/mm/
-core-$(CONFIG_NET) += arch/arm64/net/
-core-$(CONFIG_KVM) += arch/arm64/kvm/
-core-$(CONFIG_XEN) += arch/arm64/xen/
-core-$(CONFIG_CRYPTO) += arch/arm64/crypto/
+core-y		+= arch/arm64/
 libs-y		:= arch/arm64/lib/ $(libs-y)
 core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a