Change OpenWRT imported dtsi files

Change '#include <fbsd-*>' to '/include/ "fbsd-*"' in [rm]t*.dtsi

Basically the pre-import work on OpenWRT's dts/dtsi files boils down to:

for f in ls [mr]t*.dtsi; do
printf '\n/include/ "fbsd-$f"\n' >> $f
done

Approved by: adrian (mentor)
Sponsored by: Smartcom - Bulgaria AD
Differential Revision: https://reviews.freebsd.org/D5993