ramips: mt7620: add DIR-810L's mt7610e 5 GHz radio
The 5 GHz radio of this device uses an mt7610e pci-e chip, which has
been recently added support.
Tested on the actual device as AP and client, TCP throughput ~90 Mbps
U/D.
Signed-off-by: Roger Pueyo Centelles <[email protected]>