net: dsa: b53: update PCS driver to use neg_mode

Update B53'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>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/E1qA8Ee-00EaGL-Az@rmk-PC.armlinux.org.uk


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