intel: Move the draw_x/draw_y to the renderbuffer where it belongs.

intel: Move the draw_x/draw_y to the renderbuffer where it belongs.

It was originally located in the region because the tracking of
depth/color buffers was on the regions, and getting back to the irb
would have been tricky.  Now, we're keying off of the renderbuffer in
more places, which means we can move these fields where they belong.

This could fix potential rendering failure with a single texture
having multiple images attached to different renderbuffers across
shareCtx (as far as I can tell, this was the only failure we could
cause, since anything else should trigger intel_render_texture in
between, for example a BindFramebuffer).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad@chad-versace.us>