gianfar: do not advertise any alarm capability.

An early draft of the PHC patch series included an alarm in the
gianfar driver. During the review process, the alarm code was dropped,
but the capability removal was overlooked. This patch fixes the issue
by advertising zero alarms.

This patch should be applied to every 3.x stable kernel.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Reported-by: Chris LaRocque <clarocq@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>