ptp_qoriq: make ptp operations global

This patch is to make functions of ptp operations global,
so that ENETC PTP driver which is a PCI driver for same
1588 timer IP block could reuse them.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>