UPSTREAM: drm/virtio: track virtual output state

Track whenever an virtual output (crtc) is enabled or disabled.

On atomic updates check for both framebuffer being present and crtc
being enabled to figure whenever the output is active or not.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180813152855.12863-1-kraxel@redhat.com


(cherry picked from commit 6c19787e10b1bb99abbc3d257156c22bea5ca5b1)
Signed-off-by: Greg Hartman <ghartman@google.com>
BUG: 139386237
Change-Id: I2957c2793f14a77ddf7084ade9b360ee40509dcb