The GMAC1 controller in the RZN1 IP requires the RX MII clock signal to be
started before it initializes its own hardware, thus before it calls
phylink_start.

Implement the pcs_pre_init() callback so that the RX clock signal can be
enabled early if necessary.
Reported-by: Clément Léger <clement.leger@bootlin.com>
Link: https://lore.kernel.org/linux-arm-kernel/20230116103926.276869-4-clement.leger@bootlin.com/Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240326-rxc_bugfix-v6-7-24a74e5c761f@bootlin.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>