MAINTAINERS: add Dan Streetman to zswap maintainers

Add myself as zswap maintainer.

Link: http://lkml.kernel.org/r/20170124212200.19052-1-ddstreet@ieee.org
Signed-off-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Seth Jennings <sjenning@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -13679,6 +13679,7 @@ F:	Documentation/vm/zsmalloc.txt
 
 ZSWAP COMPRESSED SWAP CACHING
 M:	Seth Jennings <sjenning@redhat.com>
+M:	Dan Streetman <ddstreet@ieee.org>
 L:	linux-mm@kvack.org
 S:	Maintained
 F:	mm/zswap.c