net/mlx5: fix timestamp initialization on empty clock queue

net/mlx5: fix timestamp initialization on empty clock queue

The committing completions by clock queue might be delayed
after queue initialization is done and the only Clock Queue
completion entry (CQE) might keep the invalid status till
the CQE first update happens.

The mlx5_txpp_update_timestamp() wrongly recognized invalid
status as error and reported about lost synchronization.

The patch recognizes the invalid status as "not updated yet"
and accurate scheduling initialization routine waits till
CQE first update happens.

Some collateral typos in comment are fixed as well.

Fixes: 77522be0a56d ("net/mlx5: introduce clock queue service routine")
Cc: stable@dpdk.org
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>