net: stmmac: use PCS supported_interfaces

Use the PCS' supported_interfaces member to build the MAC level
supported_interfaces bitmap.

Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tTfff-007Roc-Ff@rmk-PC.armlinux.org.uk


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