linux-phytec-ti

kbuild: specify modules(_install) as PHONY rather than FORCE

As in other places, PHONY is a better fit for "modules" and
"modules_install".

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Michal Marek <mmarek@suse.com>