anv: Reduce the minimum number of relocations

The original value of 256 was under the assumption that you're a batch
buffer which is likely going to have a large number of relocations.
However, pipeline objects on Gen7 will have at most 6 relocations (one
per shader stage and one for the workaround BO) so this is a lot of
per-pipeline wasted space.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/intel/vulkan/anv_batch_chain.c

@@ -118,7 +118,7 @@ anv_reloc_list_grow(struct anv_reloc_list *list,
    if (list->num_relocs + num_additional_relocs <= list->array_length)
       return VK_SUCCESS;
 
-   size_t new_length = MAX2(256, list->array_length * 2);
+   size_t new_length = MAX2(16, list->array_length * 2);
    while (new_length < list->num_relocs + num_additional_relocs)
       new_length *= 2;