MAINTAINERS: update mtd-physmap.yaml reference

Changeset 63f8e9e0 ("dt-bindings: mtd: Convert mtd-physmap to DT schema")
renamed: Documentation/devicetree/bindings/mtd/arm-versatile.txt
    and: Documentation/devicetree/bindings/mtd/cypress,hyperflash.txt
to: Documentation/devicetree/bindings/mtd/mtd-physmap.yaml.

Update their cross-references accordingly.

Fixes: 63f8e9e0 ("dt-bindings: mtd: Convert mtd-physmap to DT schema")
Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/cdf3891ef686eca67c6072da8c1d027eedc1ef3e.1634630486.git.mchehab+huawei@kernel.org