net: phy: micrel: add MDI/MDI-X control support for KSZ9477 switch-integrated PHYs

net: phy: micrel: add MDI/MDI-X control support for KSZ9477 switch-integrated PHYs

Add MDI/MDI-X configuration support for PHYs integrated in the KSZ9477
family of Ethernet switches.

All MDI/MDI-X configuration modes are supported:
  - Automatic MDI/MDI-X (ETH_TP_MDI_AUTO)
  - Forced MDI (ETH_TP_MDI)
  - Forced MDI-X (ETH_TP_MDI_X)

However, when operating in automatic mode, the PHY does not expose the
resolved crossover status (i.e., whether MDI or MDI-X is active).
Therefore, in auto mode, the driver reports ETH_TP_MDI_INVALID as
the current status.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250610091354.4060454-2-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>