mesa: set TargetIndex in VDPAURegister*SurfaceNV (v2)

We initialized Target, but not TargetIndex.
This is required since 7d7dd18711.

v2: do it in the right place. Noticed by Brian Paul.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92645

Reviewed-by: Brian Paul <brianp@vmware.com>

src/mesa/main/vdpau.c

@@ -163,9 +163,10 @@ register_surface(struct gl_context *ctx, GLboolean isOutput,
          return (GLintptr)NULL;
       }
 
-      if (tex->Target == 0)
+      if (tex->Target == 0) {
          tex->Target = target;
-      else if (tex->Target != target) {
+         tex->TargetIndex = _mesa_tex_target_to_index(ctx, target);
+      } else if (tex->Target != target) {
          _mesa_unlock_texture(ctx, tex);
          free(surf);
          _mesa_error(ctx, GL_INVALID_OPERATION,