cxgb4: Add PHY firmware support for T420-BT cards

Add support for flashing 10GBaseT adapter with BCM 84834 PHY and
Aquantia AQ1202 PHY.

Updating of the PHY firmware must happen before the INITIALIZE_CMD.

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>