wl1271: get pspoll and nullfunc templates from mac80211

mac80211 now can create pspoll and nullfunc templates, better to use those.

Signed-off-by: Kalle Valo <kalle.valo@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>