staging: brcm80211: get rid on IS_CFG80211_FAVORITE macro

cfg80211 module is always favorite for the brcmfmac driver so the
macro is not needed to know the answer.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>