brcm80211: smac: use sk_buff list for handling frames in receive path

In the receive path the frames are obtained from the dma using
multiple sk_buff that were linked using the skb next pointer.
This has been changed and it now used sk_buff lists and skb_queue
functions instead.

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>