qede: Handle infinite driver spinning for Tx timestamp.

In PTP Tx implementation, driver kept scheduling a poll thread until the
timestamp is available. In the error scenarios (e.g. app requesting the
timestamp for non-ptp packet), this thread kept waiting for the timestamp
forever.  This patch add changes to report such scenario as an error and
terminate the thread. Added a timeout of 2 seconds i.e., max time to wait
for Tx timestamp. Added a stat value ptp_skip_txts for reporting the number
of packets for which Tx timestamping is skipped.

Signed-off-by: Sudarsana Reddy Kalluru <skalluru@marvell.com>
Signed-off-by: Michal Kalderon <mkalderon@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>