ixp4xx_eth: Support the get_ts_info ethtool method.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/ptp/ptp_ixp46x.c b/drivers/ptp/ptp_ixp46x.c
index 6f2782b..9d13a71 100644
--- a/drivers/ptp/ptp_ixp46x.c
+++ b/drivers/ptp/ptp_ixp46x.c
@@ -284,6 +284,7 @@
 {
 	free_irq(MASTER_IRQ, &ixp_clock);
 	free_irq(SLAVE_IRQ, &ixp_clock);
+	ixp46x_phc_clock = -1;
 	ptp_clock_unregister(ixp_clock.ptp_clock);
 }
 
@@ -302,6 +303,8 @@
 	if (IS_ERR(ixp_clock.ptp_clock))
 		return PTR_ERR(ixp_clock.ptp_clock);
 
+	ixp46x_phc_clock = ptp_clock_index(ixp_clock.ptp_clock);
+
 	__raw_writel(DEFAULT_ADDEND, &ixp_clock.regs->addend);
 	__raw_writel(1, &ixp_clock.regs->trgt_lo);
 	__raw_writel(0, &ixp_clock.regs->trgt_hi);