drm/amdgpu: add virtual display support for raven

Same as other asics.  If enabled, exposes a user selectable
number of virtual displays.

Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Alex Deucher 2017-06-02 14:52:18 -04:00
commit d67fed1618