iris/gen11+: Move flush for render target change

iris/gen11+: Move flush for render target change

When starting a BLORP operation, we do the BTI-change flush.  However,
when ending it and transitioning back to regular drawing, we change the
render target again - without a set_framebuffer_state() call.  We need
to do the BTI flush there too.  BLORP flags IRIS_DIRTY_RENDER_BUFFER
now, which will cause the next draw to get the BTI flush again.

(explanation of fix by Ken)

Fixes: 2b956a093a1 ("iris: totally untested icelake support")
Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>