net: stmmac: dwmac-socfpga: use pcs_init/pcs_exit

Use the newly introduced pcs_init() and pcs_exit() operations to
create and destroy the PCS instance at a more appropriate moment during
the driver lifecycle, thereby avoiding publishing a network device to
userspace that has not yet finished its PCS initialisation.

There are other similar issues with this driver which remain
unaddressed, but these are out of scope for this patch.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
[rgantois: removed second parameters of new callbacks]
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Reviewed-by: Hariprasad Kelam <hkelam@marvell.com>
Link: https://lore.kernel.org/r/20240513-rzn1-gmac1-v7-5-6acf58b5440d@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>