MAINTAINERS: fix reference to net phy ABI file

The file sysfs-bus-mdio got removed in favor of sysfs-class-net-phydev,
with contained a duplicated set of information.

Fixes: a6cd0d2d ("Documentation: net-sysfs: Remove duplicate PHY device documentation")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

MAINTAINERS

@@ -6071,7 +6071,7 @@ M:	Florian Fainelli <f.fainelli@gmail.com>
 M:	Heiner Kallweit <hkallweit1@gmail.com>
 L:	netdev@vger.kernel.org
 S:	Maintained
-F:	Documentation/ABI/testing/sysfs-bus-mdio
+F:	Documentation/ABI/testing/sysfs-class-net-phydev
 F:	Documentation/devicetree/bindings/net/ethernet-phy.yaml
 F:	Documentation/devicetree/bindings/net/mdio*
 F:	Documentation/networking/phy.rst