ramips: use the ralink,mtd-eeprom device tree property

Use the ralink,mtd-eeprom instead of invoking the userspace firmware
loader.

Set the label and compatible string according to the the PCI binding
documentation.

Use the wifi@0,0 label and the pci0,0 compatible string in case the
PCI vendor and device id is unknown. It should work anyway since the
compatible string isn't evaluated (yet).

This commit might fixes the PCIe wireless for the Buffalo WHR-600D.
This board was mentioned in the board 10-rt2x00-eeprom firmware hotplug
script but never had the correct eeprom name set to trigger the
firmware from flash extraction.

Use the usual eeprom for the soc wmac of the Dovado Tiny AC.

Signed-off-by: Mathias Kresin <dev@kresin.me>