powerpc/vdso64: remove meaningless vgettimeofday.o build rule

VDSO64 is only built for the 64-bit kernel, hence vgettimeofday.o is
built by the generic rule in scripts/Makefile.build.

This line does not provide anything useful.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201223171142.707053-2-masahiroy@kernel.org

arch/powerpc/kernel/vdso64/Makefile

@@ -32,8 +32,6 @@ asflags-y := -D__VDSO64__ -s
 targets += vdso64.lds
 CPPFLAGS_vdso64.lds += -P -C -U$(ARCH)
 
-$(obj)/vgettimeofday.o: %.o: %.c FORCE
-
 # link rule for the .so file, .lds has to be first
 $(obj)/vdso64.so.dbg: $(src)/vdso64.lds $(obj-vdso64) $(obj)/vgettimeofday.o FORCE
 	$(call if_changed,vdso64ld_and_check)