dt-bindings: i3c: update i3c.yaml references

Changeset 5e4cdca8 ("dt-bindings: i3c: Convert the bus description to yaml")
renamed: Documentation/devicetree/bindings/i3c/i3c.txt
to: Documentation/devicetree/bindings/i3c/i3c.yaml.

Update the cross-references accordingly.

Fixes: 5e4cdca8 ("dt-bindings: i3c: Convert the bus description to yaml")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>