MAINTAINERS: add missing test files to mm gup section

We previously overlooked GUP test files that sensibly should belong to the
GUP section, include them now.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Lorenzo Stoakes <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Reviewed-by: John Hubbard <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: lorenzo-stoakes

MAINTAINERS

@@ -15795,6 +15795,10 @@ S:	Maintained
 W:	http://www.linux-mm.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
 F:	mm/gup.c
+F:	mm/gup_test.c
+F:	mm/gup_test.h
+F:	tools/testing/selftests/mm/gup_longterm.c
+F:	tools/testing/selftests/mm/gup_test.c
 
 MEMORY MANAGEMENT - KSM (Kernel Samepage Merging)
 M:	Andrew Morton <[email protected]>