mesa: Remove the Initialized field from framebuffers.

mesa: Remove the Initialized field from framebuffers.

This existed to tell the core not to call GetBufferSize, except that even
if you didn't set it nothing happened because nobody had a GetBufferSize.

v2: Remove two more instances of setting the field (from Brian)

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>