WIP: add physical_ prefix to miptree dims
WIP: change singlesample_{w,h} to logical_{w,h}
Extract function for converting from logical to physical dimensions
WIP: Move compute_msaa_layout earlier
WIP: make intel_miptree_create take logical dims

Should fix MCS being allocated too large.

Note that logical_{width,depth,height}0 are now always set.
Previously logical_{width,height}0 were only set for images created by
intel_miptree_create_for_renderbuffer, and logical_depth0 didn't
exist.
WIP: bug fix: don't allocate extra space for MCS buffer.