net: dsa: microchip: ksz8: Make flow control, speed, and duplex on CPU port configurable

Allow flow control, speed, and duplex settings on the CPU port to be
configurable. Previously, the speed and duplex relied on default switch
values, which limited flexibility. Additionally, flow control was
hardcoded and only functional in duplex mode. This update enhances the
configurability of these parameters.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20231127145101.3039399-2-o.rempel@pengutronix.de


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