i965: Avoid blocking on the GPU for setting the HiZ op vertex data.

i965: Avoid blocking on the GPU for setting the HiZ op vertex data.

We need to allocate new space every time to avoid blocking on the last
HiZ op completing.  There are two easy ways to do this:
brw_state_batch() and intel_upload_data().  brw_state_batch() is
simpler and avoids another buffer allocation.

Improves Unigine Tropics performance 0.376416% +/- 0.148722% (n=7).

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