cxgbe(4): Link related changes.

• Switch to using 32b port/link capabilities in the driver. The 32b format is used internally by firmwares > 1.16.45.0 and the driver will now interact with the firmware in its native format, whether it's 16b or 32b. Note that the 16b format doesn't have room for 50G, 200G, or 400G speeds.

• Add a bit in the pause_settings knobs to allow negotiated PAUSE settings to override manual settings.

• Ensure that manual link settings persist across an administrative down/up as well as transceiver unplug/replug.

• Remove unused is_*G_port() functions.

Approved by: re@ (gjb@)
MFC after: 1 month
Sponsored by: Chelsio Communications