Revert "anv: Stop generating weak references for instance entrypoints"

This reverts commit 00bb42105d.  It was
not as well thought out as I had intended and broke the build when
VK_KHR_display is disabled in the build.

src/intel/vulkan/anv_entrypoints_gen.py

@@ -227,6 +227,19 @@ ${strmap(device_strmap, 'device')}
  * either pick the correct entry point.
  */
 
+% for e in instance_entrypoints:
+  % if e.alias:
+    <% continue %>
+  % endif
+  % if e.guard is not None:
+#ifdef ${e.guard}
+  % endif
+  ${e.return_type} ${e.prefixed_name('anv')}(${e.decl_params()}) __attribute__ ((weak));
+  % if e.guard is not None:
+#endif // ${e.guard}
+  % endif
+% endfor
+
 const struct anv_instance_dispatch_table anv_instance_dispatch_table = {
 % for e in instance_entrypoints:
   % if e.guard is not None: