net: sparx5/lan969x: Add support for ethtool pause parameters

net: sparx5/lan969x: Add support for ethtool pause parameters

Implement get_pauseparam() and set_pauseparam() ethtool operations for
Sparx5 ports.  This allows users to query and configure IEEE 802.3x
pause frame settings via:

ethtool -a ethX
ethtool -A ethX rx on|off tx on|off autoneg on|off

The driver delegates pause parameter handling to phylink through
phylink_ethtool_get_pauseparam() and phylink_ethtool_set_pauseparam().

The underlying configuration of pause frame generation and reception is
already implemented in the driver; this patch only wires it up to the
standard ethtool interface, making the feature accessible to userspace.

Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/20250917-802-3x-pause-v1-1-3d1565a68a96@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>