net: dsa: mt7530: update PCS driver to use neg_mode

Update mt7530's embedded PCS driver to use neg_mode, even though it
makes no use of it or the "mode" argument. This makes the driver
consistent with converted drivers.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1qA8Ej-00EaGR-Fk@rmk-PC.armlinux.org.uk


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