kbuild: make *.mod not depend on *.o

The dependency

    $(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o

... exists because *.mod files previously contained undefined symbols,
which are computed from *.o files when CONFIG_TRIM_UNUSED_KSYMS=y.

Now that the undefined symbols are put into separate *.usyms files,
there is no reason to make *.mod depend on *.o files.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Makefile

@@ -1792,7 +1792,8 @@ ifdef single-build
 
 # .ko is special because modpost is needed
 single-ko := $(sort $(filter %.ko, $(MAKECMDGOALS)))
-single-no-ko := $(sort $(patsubst %.ko,%.mod, $(MAKECMDGOALS)))
+single-no-ko := $(filter-out $(single-ko), $(MAKECMDGOALS)) \
+		$(foreach x, o mod, $(patsubst %.ko, %.$x, $(single-ko)))
 
 $(single-ko): single_modpost
 	@: