iris: Fix aux assertion in resource_get_handle

iris_resource_get_handle currently asserts that the resource has an aux
state that is suitable for sharing. However, the caller of this function
can pass a flag to specify that it will handle flushing/resolving the
resource as needed for sharing. Take this flag into account when
asserting the state of the aux buffer.

Fixes: e81392868e ("iris/resource: Drop redundant checks for aux support")
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/128
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/1371>
(cherry picked from commit 3cf6325e72)

.pick_status.json

@@ -2137,7 +2137,7 @@
         "description": "iris: Fix aux assertion in resource_get_handle",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": "e81392868e6827360762fff38baf2c10c1f3b7f0"
     },

src/gallium/drivers/iris/iris_resource.c

@@ -1276,6 +1276,7 @@ iris_resource_get_handle(struct pipe_screen *pscreen,
 
 #ifndef NDEBUG
    enum isl_aux_usage allowed_usage =
+      usage & PIPE_HANDLE_USAGE_EXPLICIT_FLUSH ? res->aux.usage :
       res->mod_info ? res->mod_info->aux_usage : ISL_AUX_USAGE_NONE;
 
    if (res->aux.usage != allowed_usage) {