MAINTAINERS: update status for HMP, QAPI and QMP trees

This commit updates the status for the HMP, QAPI and QMP trees from
"Supported" to "Maintained".

In practice this means that patch review and pull requests may take
longer. Also, I'll rely more on reviewers such as Eric Blake so that
I'm able to send pull requests regularly.
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

MAINTAINERS

@@ -726,7 +726,7 @@ F: vl.c
 
 Human Monitor (HMP)
 M: Luiz Capitulino <lcapitulino@redhat.com>
-S: Supported
+S: Maintained
 F: monitor.c
 F: hmp.c
 F: hmp-commands.hx
@@ -758,7 +758,7 @@ T: git git://github.com/bonzini/qemu.git nbd-next
 QAPI
 M: Luiz Capitulino <lcapitulino@redhat.com>
 M: Michael Roth <mdroth@linux.vnet.ibm.com>
-S: Supported
+S: Maintained
 F: qapi/
 T: git git://repo.or.cz/qemu/qmp-unstable.git queue/qmp
 
@@ -772,7 +772,7 @@ T: git git://repo.or.cz/qemu/qmp-unstable.git queue/qmp
 
 QMP
 M: Luiz Capitulino <lcapitulino@redhat.com>
-S: Supported
+S: Maintained
 F: qmp.c
 F: monitor.c
 F: qmp-commands.hx