wireless/libertas/if_cs.c: fix memory leaks

The leak in if_cs_prog_helper() is obvious.

It looks a bit as if not freeing "fw" in if_cs_prog_real() was done
intentionally, but I'm not seeing why it shouldn't be freed.

Reported-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>