Fixes the following error:
make: *** No rule to make target `.tmp_kallsyms2.S', needed by `.tmp_kallsyms2.o'.

Problem is that make does not know it have to visit scripts before it can use $(KALLSYMS)
$(KALLSYMS) is a dependency to .tmp_kallsyms% but make suddenly complains about
.tmp_kallsyms2 for some reasons.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>