fbnic: Update FW link mode values to represent actual link modes

Make it so that the enum we use for the FW values represents actual link
modes that will be normally advertised by a link partner.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Link: https://patch.msgid.link/175028446893.625704.10103673858068429312.stgit@ahduyck-xeon-server.home.arpa


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