gianfar: fix phc index build failure

gianfar: fix phc index build failure

commit 28889b7e7818342f6c254e27b9b2c68702ab867a upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>