MAINTAINERS: update marvell,armada-3700-utmi-phy.yaml reference

MAINTAINERS: update marvell,armada-3700-utmi-phy.yaml reference

Changeset 6569d8386388 ("dt-bindings: phy: convert phy-mvebu-utmi to YAML schema")
renamed: Documentation/devicetree/bindings/phy/phy-mvebu-utmi.txt
to: Documentation/devicetree/bindings/phy/marvell,armada-3700-utmi-phy.yaml.

Update its cross-reference accordingly.

Fixes: 6569d8386388 ("dt-bindings: phy: convert phy-mvebu-utmi to YAML schema")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9342a88ed44726a1cc405470c834d746d4d0524c.1622648507.git.mchehab+huawei@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>