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 <[e-mail]>
Link: https://lore.kernel.org/r/9342a8[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

MAINTAINERS

···
 M:	Miquel Raynal <[e-mail]>
 S:	Maintained
 F:	Documentation/devicetree/bindings/phy/phy-mvebu-comphy.txt
-F:	Documentation/devicetree/bindings/phy/phy-mvebu-utmi.txt
+F:	Documentation/devicetree/bindings/phy/marvell,armada-3700-utmi-phy.yaml
 F:	drivers/phy/marvell/phy-mvebu-a3700-comphy.c
 F:	drivers/phy/marvell/phy-mvebu-a3700-utmi.c