i965: Don't allocate a 1-level texture when GL_GENERATE_MIPMAP is set.

Given that a teximage that calls us with this flag set will immediately
proceed to allocate the other levels, we can probably just go ahead and
allocate those levels now.

Reduces miptree copies in piglit by about .05%.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>

src/mesa/drivers/dri/i965/intel_tex_image.c

@@ -60,7 +60,8 @@ intel_miptree_create_for_teximage(struct brw_context *brw,
     */
    if ((intelObj->base.Sampler.MinFilter == GL_NEAREST ||
         intelObj->base.Sampler.MinFilter == GL_LINEAR) &&
-       intelImage->base.Base.Level == 0) {
+       intelImage->base.Base.Level == 0 &&
+       !intelObj->base.GenerateMipmap) {
       lastLevel = 0;
    } else {
       lastLevel = _mesa_get_tex_max_num_levels(intelObj->base.Target,