mlxbf_gige: support 10M/100M/1G speeds on BlueField-3

The BlueField-3 OOB interface supports 10Mbps, 100Mbps, and 1Gbps speeds.
The external PHY is responsible for autonegotiating the speed with the
link partner. Once the autonegotiation is done, the BlueField PLU needs
to be configured accordingly.

This patch does two things:
1) Initialize the advertised control flow/duplex/speed in the probe
   based on the BlueField SoC generation (2 or 3)
2) Adjust the PLU speed config in the PHY interrupt handler

Signed-off-by: David Thompson <davthompson@nvidia.com>
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>