Documentation: Hardware tag matching

Add document providing definitions of terms and core explanations
for tag matching (TM) protocols, eager and rendezvous,
TM application header, tag list manipulations and matching process.

Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Doug Ledford <dledford@redhat.com>