net: stmmac: intel: move phy_interface init to tgl_common_data()

Move the initialisation of plat->phy_interface to tgl_common_data()
as all callers set this same interface mode. This moves it to a
single location to make the change to get_interfaces() more obvious.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1uASLs-0021Qk-Qt@rmk-PC.armlinux.org.uk


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