dt: fix broken links due to txt->yaml renames

There are some new broken doc links due to yaml renames
at DT. Developers should really run:

	./scripts/documentation-file-ref-check

in order to solve those issues while submitting patches.
This tool can even fix most of the issues with:

	./scripts/documentation-file-ref-check --fix

Acked-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/0e4a7f0b7efcc8109c8a41a2e13c8adde4d9c6b9.1592203542.git.mchehab+huawei@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>