ptp: add QorIQ PTP support for ENETC

This patch is to add QorIQ PTP support for ENETC.
ENETC PTP driver which is a PCI driver for same
1588 timer IP block will reuse QorIQ PTP driver.

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