brcmfmac: remove dependency with nl80211.h

The firmware-signalling code used NL80211_NUM_ACS, but it has
its own definition enum brcmf_fws_fifo, which is more appropriate
to use. This effectively removes the need to include nl80211.h.

Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>