fbnic: Add support for reporting link config

This change adds some basic support for reporting the current link config
to the user via ethtool. Currently the main components reported are the
carrier status, link speed, and FEC.

For now we are handling the FEC directly as phylink doesn't have support
for it. The plan is to work on incorporating FEC support into phylink and
eventually adding the ability for us to set the FEC configuration through
phylink itself.

In addition as we don't yet have SFP or PHY support the listed modes
supported are including ones not supported by the media we are attached to.
That will hopefully be addressed once we can get the QSFP modules
supported.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://patch.msgid.link/175028448275.625704.60592644122010798.stgit@ahduyck-xeon-server.home.arpa


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