MAINTAINERS: notify the "Device Memory" community of memory hotplug changes

The recent episode of a warning regression in memremap_pages() [1]
highlights that relevant updates are being missed by folks that care about
core ZONE_DEVICE changes.  Yes, CXL folks should pay more attention to
linux-mm@, but it also would not hurt to copy linux-cxl@, where most
Device Memory folks hang out, on memory hotplug changes by default.

Link: http://lore.kernel.org/[email protected] [1]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Dan Williams <[email protected]>
Acked-by: Jonathan Cameron <[email protected]>
Acked-by: John Groves <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Oscar Salvador <[email protected]>
Cc: Davidlohr Bueso <[email protected]>
Cc: Dave Jiang <[email protected]>
Cc: Alison Schofield <[email protected]>
Cc: Vishal Verma <[email protected]>
Cc: Ira Weiny <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: djbw

MAINTAINERS

@@ -16428,6 +16428,7 @@ MEMORY HOT(UN)PLUG
 M:	David Hildenbrand <[email protected]>
 M:	Oscar Salvador <[email protected]>
 L:	[email protected]
+L:	[email protected]
 S:	Maintained
 F:	Documentation/admin-guide/mm/memory-hotplug.rst
 F:	Documentation/core-api/memory-hotplug.rst