pan/bi: Don't reorder image loads across stores

pan/bi: Don't reorder image loads across stores

Fixes flaking in
dEQP-GLES31.functional.image_load_store.cube.qualifiers.volatile_r32i due to
image reads being moved past a BARRIER.

To make this more robust/optimal, we probably need scheduling information
(coherent/volatile/etc) added to instructions like ACO does. That's left for a
future extension, for now I just want the test to stop flaking.

Fixes: 569e5dc7450 ("pan/bi: Schedule for pressure pre-RA")
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17841>