KVM: arm64: nvhe: Fix missing FORCE for hyp-reloc.S build rule

Add FORCE so that if_changed can detect the command line change.

We'll otherwise see a compilation warning since commit e1f86d7b
("kbuild: warn if FORCE is missing for if_changed(_dep,_rule) and
filechk").

arch/arm64/kvm/hyp/nvhe/Makefile:58: FORCE prerequisite is missing

Cc: David Brazdil <dbrazdil@google.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210907052137.1059-1-yuzenghui@huawei.com

arch/arm64/kvm/hyp/nvhe/Makefile

@@ -54,7 +54,7 @@ $(obj)/kvm_nvhe.tmp.o: $(obj)/hyp.lds $(addprefix $(obj)/,$(hyp-obj)) FORCE
 #    runtime. Because the hypervisor is part of the kernel binary, relocations
 #    produce a kernel VA. We enumerate relocations targeting hyp at build time
 #    and convert the kernel VAs at those positions to hyp VAs.
-$(obj)/hyp-reloc.S: $(obj)/kvm_nvhe.tmp.o $(obj)/gen-hyprel
+$(obj)/hyp-reloc.S: $(obj)/kvm_nvhe.tmp.o $(obj)/gen-hyprel FORCE
 	$(call if_changed,hyprel)
 
 # 5) Compile hyp-reloc.S and link it into the existing partially linked object.