net/mlx5e: Remove unused VLAN insertion logic in TX path

net/mlx5e: Remove unused VLAN insertion logic in TX path

The VLAN insertion capability (`wqe_vlan_insert`) was never enabled on
all mlx5 devices. When VLAN TX offload is advertised but this
capability is not supported, the driver uses inline headers to insert
the VLAN tag.

To support this, the driver used to set the
`MLX5E_SQ_STATE_VLAN_NEED_L2_INLINE` bit to enforce L2 inline mode
when `wqe_vlan_insert` was not supported. Since the capability is
disabled on all devices, this logic was always active, and the SQ flag
has become redundant. L2 inline is enforced unconditionally for
VLAN-tagged packets.

The `skb_vlan_tag_present()` check in the else-if block of
`mlx5e_sq_xmit_wqe()` is never true by this point in the TX flow,
as the VLAN tag has already been inserted by the driver using inline
headers. As a result, this code is never executed.

Remove the redundant SQ state, dead VLAN insertion code block, and
related logic.

Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/1752009387-13300-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>