net/mlx5e: TX, Obsolete maintaining local copies of skb->len/data

Instead of maintaining a local copy of skb->len/data and updating
it upon every copy to the WQE inline part, just calculate it once
when needed, using the ihs.

This obsoletes the function mlx5e_tx_skb_pull_inline.

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