iwlagn: move the mapping ac to queue / fifo to transport

This mapping is transport related.
This allows us to remove the notion of tx queue from the tx path in
the upper layer.
iwl_wake_any_queue moved to transport layer since it needs to access
these mappings.
The TX API is nicer now:

int (*tx)(struct iwl_trans *trans, struct sk_buff *skb,
		struct iwl_device_cmd *dev_cmd, u8 ctx, u8 sta_id);

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>