* Remove dt-utils patches applied upstream
All patches are now applied upstream. With 2021.03.0 release no more
downstream patches are required.
* Bump buildroot to fix linux-firmware build issues
* buildroot f10577b836...3c5f87185d (3):
> package/linux-firmware: add rtl8761b/rtl8761bu firmware
> package/linux-firmware: bump version to 20210919
> Revert "package/linux-firmware: add rtl8761b/rtl8761bu firmware"