This patch adds more comments to describe the structures and functions of vtd
that are public to the other components in the hypervisor. The comments are in
doxygen-style for document generation.
Tracked-On: #1595
Signed-off-by: Binbin Wu <binbin.wu@intel.com>
Reviewed-by: Geoffroy Van Cutsem <geoffroy.vancutsem@intel.com>