broadcom/compiler: handle moving last ubo load in the block correctly

Before we move a UBO load to a previous location in the block we take a
reference to the instruction after it so we can continue the loop from
there, however, if the load we just moved was already the last instruction
in the block we just want to break the loop right there.

Fixes crashes with shaders from http://flightradar24.com

Fixes: 8998666de7 ("broadcom/compiler: sort constant UBO loads by index and offset")
Reviewed-by: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35333>
(cherry picked from commit c059c721fb)

.pick_status.json

@@ -134,7 +134,7 @@
         "description": "broadcom/compiler: handle moving last ubo load in the block correctly",
         "nominated": true,
         "nomination_type": 2,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "8998666de7e827f5fe62b51186c7f81d362a2be1",
         "notes": null

src/broadcom/compiler/vir.c

@@ -1541,6 +1541,10 @@ v3d_nir_sort_constant_ubo_load(nir_block *block, nir_intrinsic_instr *ref)
                         exec_node_insert_after(&pos->node, &inst->node);
 
                 progress = true;
+
+                /* If this was the last instruction in the block we are done */
+                if (!next_inst)
+                        break;
         }
 
         return progress;