The protection requested for a given surface, must reach through the
weston_surface::pending_state, in the commit-cycle for the
weston_surface, so that it gets updated in the next commit.

As some protection is requested for a given weston_surface, it means
protection must be set for each of the outputs which show the surface.

While setting the protection of a weston_output, care must be taken
so as to avoid, degrading the protection of another surfaces, enjoying
the protection. For this purpose, all the weston_surfaces that are
shown on a weston_output are checked for their desired protection.
The highest of all such desired protections must be set for the
weston_output to avoid degrading of existing protected surfaces.
A surface requesting protection for a lower content-type can still be
provided protection for a higher type but the converse cannot be
allowed.

This patch adds support to set content-protection for a suface, which
inturn sets the content-protection for each of the outputs on which
it is shown, provided, none of the existing surface's protection
request is downgraded.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>