radv: Use a sort for rebuilding the sparse buffer bo list.

radv: Use a sort for rebuilding the sparse buffer bo list.

It uses slightly more memory (though still bounded by the number
of mapped ranges), but gives less quadratic behavior.

Cuts 4 minutes from the runtime of the CTS *.sparse.* tests.

Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>