brcm80211: fmac: add frame header extension support

A header extension is introduced in the received frame to provide
extra space for dongle information. This won't affect current
supported chipset since the data_offset is 0. But it's necessary for
adding support for future chipset.
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/brcm80211/brcmfmac/dhd_cdc.c

@@ -421,6 +421,7 @@ int brcmf_proto_hdrpull(struct device *dev, int *ifidx,
 	pktbuf->priority = h->priority & BDC_PRIORITY_MASK;
 
 	skb_pull(pktbuf, BDC_HEADER_LEN);
+	skb_pull(pktbuf, h->data_offset << 2);
 
 	return 0;
 }