vk/device: Use bias rather than layers for computing binding table size

Because we statically use the first 8 binding table entries for render
targets, we need to create a table of size 8 + surfaces.

src/vulkan/device.c

@@ -2274,7 +2274,7 @@ flush_descriptor_sets(struct anv_cmd_buffer *cmd_buffer)
          struct anv_state state;
          uint32_t size;
 
-         size = (layers + surface_count) * sizeof(uint32_t);
+         size = (bias + surface_count) * sizeof(uint32_t);
          state = anv_state_stream_alloc(&cmd_buffer->surface_state_stream, size, 32);
          memcpy(state.map, bindings->descriptors[s].surfaces, size);