octeontx2-pf: Add support for PTP clock

This patch adds PTP clock and uses it in Octeontx2
network device. PTP clock uses mailbox calls to
access the hardware counter on the RVU side.

Co-developed-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Aleksey Makarov <amakarov@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>