Since commit 6f2e1b7485 (ath79: disable delays on AT803X config init)
the incoming incoming traffic on the ubnt,lap-120 devices Ethernet
port was not making it through. Using rgmii-id instead of rgmii (same
configuration as ubnt,litebeam-ac-gen2) fixes it.
Fixes FS#2893.
Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>