cxgb4: avoid disabling FEC by default

Recent Chelsio firmware started using few port capablity bits to
manage FEC and as driver was not aware of FEC changes those bits
were zeroed, consequently disabling FEC.

Avoid zeroing those bits and default to whatever the firmware
tells us the Link is currently advertising.

Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>