ceph: show tasks waiting on caps in debugfs caps file

[ Upstream commit 3a3430af ]

Add some visibility of tasks that are waiting for caps to the "caps"
debugfs file. Display the tgid of the waiting task, inode number, and
the caps the task needs and wants.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Stable-dep-of: e7e607bd ("ceph: defer stopping mdsc delayed_work")
Signed-off-by: Sasha Levin <sashal@kernel.org>