i965: Initial Ivybridge Viewport state setup.

i965: Initial Ivybridge Viewport state setup.

SF and CLIP viewport state has been combined into SF_CLIP_VIEWPORT;
SF_CLIP and CC state pointers can now be uploaded independently.

Some portions of the hardware documentation refer to separate upload
commands for SF and CLIP; these are outdated and incorrect.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Eric Anholt <eric@anholt.net>