net/mlx5e: Rename timestamp fields to hwtstamp_config

net/mlx5e: Rename timestamp fields to hwtstamp_config

Rename hardware timestamp-related fields from 'tstamp' to
'hwtstamp_config' throughout the MLX5 driver. The new name is more
descriptive as it clearly indicates these fields contain hardware
timestamp configuration.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1761819910-1011051-5-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>