MAINTAINERS: update intel,ixp46x-rng.yaml reference

MAINTAINERS: update intel,ixp46x-rng.yaml reference

The file name: Documentation/devicetree/bindings/display/intel,ixp46x-rng.yaml
should be, instead: Documentation/devicetree/bindings/rng/intel,ixp46x-rng.yaml.

Update its cross-reference accordingly.

Fixes: f0d519e7e55a ("hw_random: ixp4xx: Add DT bindings")
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/70a3d6696de52a3d6112adbf7247a4b4ae9c7e11.1634630486.git.mchehab+huawei@kernel.org