wil6210: fix mapping packets to invalid queue

wil_select_queue() returns invalid queue id (7) for special packets.
Fix this by setting skb->priority = 7 which in turn will return
correct queue id.

Change-Id: Ia2013a6fcf736128815cecb4f466ee43f3fd7afd
Signed-off-by: Ahmad Masri <amasri@codeaurora.org>