freedreno/ir3: Use LDIB for coherent image loads on a5xx.

freedreno/ir3: Use LDIB for coherent image loads on a5xx.

If the coherent flag is present, then we need to not have an incoherent
cache between us and previous stores to the image that were also decorated
as coherent.  isam apparently (unsurprisingly) goes through a texture
cache.  Use ldib instead, so that we don't get the wrong result.

We would need a similar fix for a4xx, but that uses ldgb and I don't
have hardware to test on.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12704>