net/mlx5e: TX, Inline TLS skb check

When TLS is supported and enabled, every transmitted packet is tested
to identify if TLS offload is required.

Take the early-return condition into an inline function, to save
the overhead of a function call for non-TLS packets.

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