cxgb4: Allocate Tx queues dynamically

Allocate resources dynamically for Upper layer driver's (ULD) like
cxgbit, iw_cxgb4, cxgb4i and chcr. The resources allocated include Tx
queues which are allocated when ULD register with cxgb4 driver and freed
while un-registering. The Tx queues which are shared by ULD shall be
allocated by first registering driver and un-allocated by last
unregistering driver.

Signed-off-by: Atul Gupta <atul.gupta@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>