fbnic: Add support for setting/getting pause configuration

Phylink already handles most of the pieces necessary for configuring
autonegotation. With that being the case we can add support for
getting/setting pause now by just passing through the ethtool call to the
phylink code.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/175028448974.625704.14427543910503058114.stgit@ahduyck-xeon-server.home.arpa


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