staging: brcm80211: change packet buffer type to native struct sk_buff

The packet queues now store struct sk_buff pointer and subsequently
all driver code handling packets now use struct sk_buff as package
storage type. Next step will be getting rid of packet macros.

Reviewed-by: Brett Rudley <brudley@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>