i965: Emit invariant state once at startup on Gen6+.

i965: Emit invariant state once at startup on Gen6+.

Now that we have hardware contexts, we can safely initialize our GPU
state once at startup, rather than needing a state atom with the
BRW_NEW_CONTEXT flag set.

This removes a tiny bit of code from our drawing loop.

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