kbuild: drop FORCE from PHONY targets

These targets are marked as PHONY.  No need to add FORCE to their
dependency.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.com>
diff --git a/arch/arm/vdso/Makefile b/arch/arm/vdso/Makefile
index 1160434..59a8fa7 100644
--- a/arch/arm/vdso/Makefile
+++ b/arch/arm/vdso/Makefile
@@ -74,5 +74,5 @@
 	@mkdir -p $(MODLIB)/vdso
 
 PHONY += vdso_install
-vdso_install: $(obj)/vdso.so.dbg $(MODLIB)/vdso FORCE
+vdso_install: $(obj)/vdso.so.dbg $(MODLIB)/vdso
 	$(call cmd,vdso_install)