dt-bindings: reserved-memory: ramoops: update ramoops.yaml references

Changeset 89a5bf0f ("dt-bindings: reserved-memory: ramoops: Convert txt bindings to yaml")
renamed: Documentation/devicetree/bindings/reserved-memory/ramoops.txt
to: Documentation/devicetree/bindings/reserved-memory/ramoops.yaml.

Update the cross-references accordingly.

Fixes: 89a5bf0f ("dt-bindings: reserved-memory: ramoops: Convert txt bindings to yaml")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/bccd9c181b68a1ebbaefd5dcce63e1b8a4b1596c.1634630486.git.mchehab+huawei@kernel.org