anv: Flush render cache before STATE_BASE_ADDRESS on gen7

anv: Flush render cache before STATE_BASE_ADDRESS on gen7

We had no good reason for *not* doing this on gen7 before but we didn't
know it was needed.  Recently, when trying update to Vulkan CTS version
1.0.2 in our CI system, Mark discovered GPU hangs on Haswell that appear
to be STATE_BASE_ADDRESS related.  This commit fixes them.

Reported-by: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "13.0 17.0" <mesa-stable@lists.freedesktop.org>