kbuild: remove append operation on cmd_ld_ko_o

The append operation was introduced in
commit b1a1a1a09b46 ("kbuild: lto: postpone objtool")
when the command was created from two parts.
In commit 850ded46c642 ("kbuild: Fix TRIM_UNUSED_KSYMS with LTO_CLANG")
however the first part was removed again, making the append operation
unnecessary.

To keep this command definition aligned with all other command
definitions, remove the append again.

Signed-off-by: Thomas Weißschuh <[e-mail]>
Signed-off-by: Masahiro Yamada <[e-mail]>

scripts/Makefile.modfinal

···
 	$(call if_changed_dep,cc_o_c)
 
 quiet_cmd_ld_ko_o = LD [M]  $@
-      cmd_ld_ko_o +=							\
+      cmd_ld_ko_o =							\
 	$(LD) -r $(KBUILD_LDFLAGS)					\
 		$(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)		\
 		-T scripts/module.lds -o $@ $(filter %.o, $^)