A careful reading of the MKL documentation on ?potrf and packed storage shows that there is no place for row-major or column-major packed storage issues. The concepts of row- or column-major apply only to arrays of rank greater than 1.
There is only one convention for packed storage, and that is by columns. If one is storing a lower triangular matrix, the packed 1-D array contains n elements from col-1, then n-1 elements from col-2,..., 1 element from col-n. If storing an upper triangular matrix, the packed 1-D array contains 1 element from col-1, then 2 from col-2,..., n elements from col-n.