intel: Convert to untiled pitches if surface is too large for tiling.

intel: Convert to untiled pitches if surface is too large for tiling.

If the pitch is too large for the hardware to tile, recompute the
required surface size based on the untiled pitch and alignments. For the
older hardware, which has smaller limits and greater restrictions, this
may be a considerable saving in allocation size.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>