MAINTAINERS: add HMM selftests

Add files for HMM selftests.

Link: https://lore.kernel.org/r/20200422195028.3684-4-rcampbell@nvidia.comSigned-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

MAINTAINERS

@@ -7732,7 +7732,9 @@ L:	linux-mm@kvack.org
 S:	Maintained
 F:	Documentation/vm/hmm.rst
 F:	include/linux/hmm*
+F:	lib/test_hmm*
 F:	mm/hmm*
+F:	tools/testing/selftests/vm/*hmm*
 
 HOST AP DRIVER
 M:	Jouni Malinen <j@w1.fi>