i965/blorp: Make post draw flush more explicit

i965/blorp: Make post draw flush more explicit

Blits do not need any special treatment as the target buffer
object is added to render cache just as one does for normal draw.
Color clears and resolves in turn require explicit "end of pipe
synchronization". It is not clear what this means exactly but the
assumption is that render cache flush with command stream stall
should be sufficient.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>