mac80211: make rc_pid_fop_events static

No need to not be.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Acked-by: Stefano Brivio <stefano.brivio@polimi.it>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>