Fill in the possible_interfaces member.
GPY21x phys support the SGMII and 2500base-X interfaces
Signed-off-by: Raju Lakkaraju <Raju.Lakkaraju@microchip.com>
Link: https://lore.kernel.org/r/20240216054435.22380-1-Raju.Lakkaraju@microchip.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>