qede: Add support for PTP resource locking.

The patch adds necessary changes to the driver to use qed resource
locking functionality. Currently the ptp initialization is spread
between driver probe/open implementations, associated APIs are
qede_ptp_register_phc()/qede_ptp_start(). Clubbed this functionality
into single API qed_ptp_enable() to simplify the usage of qed resource
locking implementation. The new API will be invoked in the probe path.
Similarly the ptp clean-up code is moved to qede_ptp_disable() which
gets invoked in the driver unload path.

Signed-off-by: Sudarsana Reddy Kalluru <Sudarsana.Kalluru@cavium.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>