realtek: rtl93xx: support SFPs with phys

realtek: rtl93xx: support SFPs with phys

This driver use "phy-handle" as a placeholder for mac configuration
data.  Such handles are therefore required for all ports - even those
connected directly to SFP slots and having a managed property set to
"in-band-status".

The DSA core will register these nodes as if they are real phys. This
prevents later attachment of pluggable phys with errors like

   sfp sfp-p8: sfp_add_phy failed: -EBUSY

Replace the virtual SFP slot handles with "pseudo-phy-handle" to keep
the driver logic as-is but hide the node from the DSA core.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
Link: https://github.com/openwrt/openwrt/pull/17950
Signed-off-by: Sander Vanheule <sander@svanheule.net>