Merge patch series "upstream DT compatibility"

Caleb Connolly <caleb.connolly@linaro.org> says:

This is a subset of [1]. With more platform maintainers switching to
OF_UPSTREAM I didn't want to get in the way (it has also proven more
difficult than I hoped to remove only the fully compatible header
files).

This series removes only the dt-bindings headers which contain generic
data like GPIO flags, input event codes, etc.

It then implements support for building all DTBs for a vendor with
OF_UPSTREAM_BUILD_VENDOR. This removes the need to maintain a set list
of DTBs that can be built by U-Boot and opens up the possibility of new
boards becoming supported "by default" just by landing their DT
upstream.

[1]: https://lore.kernel.org/u-boot/20240321-b4-upstream-dt-headers-v2-0-1eac0df875fe@linaro.org