kbuild: refactor part-of-module more

# ---------------------------------------------------------------------------

# Default is built-in, unless we know otherwise

$(foreach x, i ll lst o s symtypes, $(patsubst %.o,%.$(x),$(real-obj-m))): \

	part-of-module := y

part-of-module = $(if $(filter $(basename $@).o, $(real-obj-m)),y)

modkern_cflags =                                          \

	$(if $(part-of-module),                           \