tools: bpf: cleanup PHONY target

There is no FORCE target in the Makefile and some of the PHONY
targets are missing, update the list.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

tools/bpf/Makefile

@@ -100,4 +100,4 @@ bpftool_install:
 bpftool_clean:
 	$(call descend,bpftool,clean)
 
-.PHONY: bpftool FORCE
+.PHONY: all install clean bpftool bpftool_install bpftool_clean