cxgb4: get on-chip queue info from FW and create a memory window for them

Get info about the availability of Tx on-chip queues from FW and if they
are supported set up a memory window for them.  iw_cxgb4 will be using them.
Move the existing window setup later in the init sequence, after we have
collected the new info.

Signed-off-by: Dimitris Michailidis <dm@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>