UPSTREAM: mm/damon/dbgfs: fix memory leak when using debugfs_lookup()

When calling debugfs_lookup() the result must have dput() called on it,
otherwise the memory will leak over time.  Fix this up by properly calling
dput().

Bug: 254441685
Link: https://lkml.kernel.org/r/20220902191149.112434-1-sj@kernel.org


Fixes: 75c1c2b5 ("mm/damon/dbgfs: support multiple contexts")
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 1552fd3e)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ib7cfad2c9d32d185ff8267c3d421dd2426e36eb8