dt-bindings: net: add schema for Microchip/SMSC LAN95xx USB Ethernet controllers

dt-bindings: net: add schema for Microchip/SMSC LAN95xx USB Ethernet controllers

Create initial schema for Microchip/SMSC LAN95xx USB Ethernet controllers and
import some of currently supported USB IDs form drivers/net/usb/smsc95xx.c

These devices are already used in some of DTs. So, this schema makes it official.
NOTE: there was no previously documented txt based DT binding for this
controllers.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220517111505.929722-3-o.rempel@pengutronix.de