doc: remove warning "file not included in toctree"

Files that are included directly into other files are not referenced
in TOC trees. Quiet warning by tagging them :orphan:

Change-Id: I3a975420ce366ca155e8c0158dcd0fb7c094a4a0
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
8 files changed