MAINTAINERS, SLAB: add Roman as reviewer, git tree

The slab code has an overlap with kmem accounting, where Roman has done
a lot of work recently and it would be useful to make sure he's CC'd on
patches that potentially affect it.  Thus add him as a reviewer for the
SLAB subsystem.

Also while at it, add the link to slab git tree.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>
Acked-by: David Rientjes <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: tehcaster

MAINTAINERS

@@ -17762,8 +17762,10 @@ M:	David Rientjes <[email protected]>
 M:	Joonsoo Kim <[email protected]>
 M:	Andrew Morton <[email protected]>
 M:	Vlastimil Babka <[email protected]>
+R:	Roman Gushchin <[email protected]>
 L:	[email protected]
 S:	Maintained
+T:	git git://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git
 F:	include/linux/sl?b*.h
 F:	mm/sl?b*