MAINTAINERS: Move MFD from a Supported to Maintaied state

No one is funding MFD maintenance.

  S: *Status*, one of the following:
     Supported:   Someone is actually paid to look after this.
     Maintained:  Someone actually looks after it.
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221206105038.124613-1-lee@kernel.org

MAINTAINERS

@@ -14280,7 +14280,7 @@ F:	drivers/media/i2c/mt9v111.c
 
 MULTIFUNCTION DEVICES (MFD)
 M:	Lee Jones <lee@kernel.org>
-S:	Supported
+S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lee/mfd.git
 F:	Documentation/devicetree/bindings/mfd/
 F:	drivers/mfd/