net: phy: marvell10g: fill in possible_interfaces

Fill in the possible_interfaces member according to the selected
mactype mode.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/E1r6VHv-00DDLZ-OL@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>