net/mlx5e: Add states to PTP channel

Add PTP TX state to PTP channel, which indicates the corresponding SQ is
available. Further patches in the set extend PTP channel to include RQ.
The PTP channel state will be used for separation and coexistence of RX
and TX PTP. Enhance conditions to verify the TX PTP state is set.

Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>