patches/openwrt: Turris 1.x support patch: fix board naming

It seems that we are not using "fsl,P2020RDB" anymore as we change it to
"cznic,turris1x" with a new DTS.

Fixes: 9e0a337d ("patches/openwrt:
Turris 1.x: new Device Tree")
7 jobs for fix/turris1x-patch in 6 minutes and 6 seconds (queued for 5 seconds)