intel: Avoid making tiled miptrees we won't be able to blit.

intel: Avoid making tiled miptrees we won't be able to blit.

Doing so was breaking miptree mapping, which we really need to be able to
handle.  With this change, intel_miptree_map_direct() falls through to
doing a CPU mapping on the buffer like we need.

With the previous 2 patches, all of these should be fixed:
piglit max-texture-size (all 3 patches required!)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=37871
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44958
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=53494

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>