fbnic: Set correct supported modes and speeds based on FW setting

The fbnic driver was using the XLGMII link mode to enable phylink, however
that mode wasn't the correct one to use as the NIC doesn't actually use
XLGMII, it is using a combinations of 25G, 50G, and 100G interface modes
and configuring those via pins exposed on the PCS, MAC, and PHY interfaces.
To more accurately reflect that we should drop the uxe of XGMII and XLGMII
and instead use the correct interface types.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://patch.msgid.link/175028447568.625704.17971496887030109107.stgit@ahduyck-xeon-server.home.arpa


Signed-off-by: Paolo Abeni <pabeni@redhat.com>