include: phy: define XFI and USXGMII interface types

include: phy: define XFI and USXGMII interface types

Drivers currently use XGMII for XFI and USXGMII and, where needed, use
other information to identify the actual protocol on the board.  With these
two defined drivers can now rely on DT phy-mode property.

Signed-off-by: Alex Marginean <alexandru.marginean@nxp.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>