ptp_qoriq: drop the code of alarm

The alarm function hadn't been supported by PTP clock driver.
The recommended solution PHC + phc2sys + nanosleep provides
best performance. So drop the code of alarm in ptp_qoriq driver.

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