arm-autonomy: Create meta-arm-autonomy layer

Create a meta-arm-autonomy layer in meta-arm.
Add layer configuration file and Readme.

Change-Id: Idf3411edc21f3d13fdc7146fcf34700d2aab1c41
Issue-Id: SCM-767
Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>