ptp: ravb: convert to .adjfine and adjust_by_scaled_ppm

The ravb implementation of .adjfreq is implemented in terms of a
straight forward "base * ppb / 1 billion" calculation.

Convert this driver to .adjfine and use the adjust_by_scaled_ppm helper
function to calculate the new addend.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Cc: Sergey Shtylyov <s.shtylyov@omp.ru>
Cc: Biju Das <biju.das.jz@bp.renesas.com>
Cc: Phil Edworthy <phil.edworthy@renesas.com>
Cc: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Cc: linux-renesas-soc@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>