mips: dts: ralink: add MT7621 SoC

The MT7621 system-on-a-chip includes an 880 MHz MIPS1004Kc dual-core CPU,
a 5-port 10/100/1000 switch/PHY and one RGMII.

Add the devicetrees for GB-PC1 and GB-PC2 devices which use MT7621 SoC.

Acked-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Link: https://lore.kernel.org/r/20220315160149.3617-1-arinc.unal@arinc9.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>