net: dsa: mt7530: mark as non-legacy

The mt7530 driver does not make use of the speed, duplex, pause or
advertisement in its phylink_mac_config() implementation, so it can be
marked as a non-legacy driver.

Tested-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>