intel: Make a temporary miptree for the blit path of miptree mapping.

intel: Make a temporary miptree for the blit path of miptree mapping.

In a bit of debug code, we no longer have the inter-slice x/y to print.
But I think the level/slice is more useful in this case for looking at
what's getting mapped, especially given that INTEL_DEBUG=blit will tell
you the other value.

Reviewed-and-tested-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>