gianfar: fix phc index build failure

This patch fixes a build failure introduced in commit 66636287
("gianfar: Support the get_ts_info ethtool method."). Not only was a
global variable inconsistently named, but also it was not exported as
it should have been.

This fix is also needed in stable version 3.5.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/freescale/gianfar_ethtool.c b/drivers/net/ethernet/freescale/gianfar_ethtool.c
index 8971921..ab6762c 100644
--- a/drivers/net/ethernet/freescale/gianfar_ethtool.c
+++ b/drivers/net/ethernet/freescale/gianfar_ethtool.c
@@ -1773,6 +1773,7 @@
 }
 
 int gfar_phc_index = -1;
+EXPORT_SYMBOL(gfar_phc_index);
 
 static int gfar_get_ts_info(struct net_device *dev,
 			    struct ethtool_ts_info *info)