get rid of magic in proc_namespace.c

don't rely on proc_mounts->m being the first field; container_of()
is there for purpose.  No need to bother with ->private, while
we are at it - the same container_of will do nicely.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
(cherry picked from commit 6ce6e24e72233073c8ead9419fc5040d44803dae)
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>

Change-Id: I1ad6bc2de94a6b2efa110c5ebb76615fb67ef3d1
3 files changed