staging: brcm80211: fixed double #include problem

Code cleanup. Removed one redundant include and reshuffled #include order as
to include Linux header files first.

Reported-by: julie Sullivan <kernelmail.jms@gmail.com>
Signed-off-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>