When a resource is written by a compute shader and then used by a
non-compute stage we sync on last compute job to guarantee that the
resource has been completely written when the next stage reads resources.

In the other cases how flushes are done guarantee the serialization of
the writes and reads.

To reproduce the failure the following tests should be executed in batch
as last test don't fail when run isolated:

KHR-GLES31.core.shader_image_load_store.basic-allFormats-load-fs
KHR-GLES31.core.shader_image_load_store.basic-allFormats-loadStoreComputeStage
KHR-GLES31.core.shader_image_load_store.basic-allTargets-load-cs
KHR-GLES31.core.shader_image_load_store.advanced-sync-vertexArray

v2: Use fence dep instead of bo_wait (Eric Anholt)
v3: Rename struct names (Iago Toral)
    Document why is not needed on graphics->compute case. (Iago Toral)
    Follow same code pattern of the other update of in_sync_bcl.
v4: Fixed comments style. (Iago Toral)

Fixes KHR-GLES31.core.shader_image_load_store.advanced-sync-vertexArray

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
CC: 19.3 20.0 <mesa-stable@lists.freedesktop.org>
Tested-by: Marge Bot <mesa!2700>
Part-of: <mesa!2700>