iris: Emit single render target flush PIPE_CONTROL on format mismatch.

iris: Emit single render target flush PIPE_CONTROL on format mismatch.

The big-hammer iris_flush_depth_and_render_caches() is largely
redundant whenever a format mismatch is detected from
iris_cache_flush_for_render().  There is no need to kick the depth,
sampler nor constant caches in that case.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3875>