VFS: Comment mount following code

Add comments describing what the directions "up" and "down" mean and ref count
handling to the VFS mount following family of functions.

Signed-off-by: Valerie Aurora <vaurora@redhat.com> (Original author)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
(cherry picked from commit f015f1267b23d3530d3f874243fb83cb5f443005)
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>

Change-Id: Idd2775e7a433b00da8f39e3f49185d03d5a58a3b
2 files changed