scripts/cocci: Rename memory-region-{init-ram -> housekeeping}

As we are going to add various semantic changes related to the memory
region API, rename this script to be more generic.
Add a 'usage' header, and an entry in MAINTAINERS to avoid checkpatch
warning.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
diff --git a/MAINTAINERS b/MAINTAINERS
index a88bc28..770126f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2047,6 +2047,7 @@
 F: memory.c
 F: include/exec/memory-internal.h
 F: exec.c
+F: scripts/coccinelle/memory-region-housekeeping.cocci
 
 SPICE
 M: Gerd Hoffmann <kraxel@redhat.com>