Return interfaces on Turris 1.x on TOS 6.0
Since kernel 5.4 in TOS 6.0, /sys/firmware/devicetree/base/model
now contain string Turris 1.x
(from DTS).
On TOS 5.x it was just Turris
.
Update the get_model()
logic to detect Turris 1.x routers on TOS 6.0.