i965/dri: Store the screen associated with the image

I intend to need to get to the devinfo structure, and storing the screen
is an easy way to do that.

It seems to be the consensus that you cannot share an image between
multiple screens.

Scape-goat: Rob Clark <robdclark@gmail.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
2 files changed