net/mlx5e: Verify inline header size do not exceed SKB linear size

Driver tries to copy at least MLX5E_MIN_INLINE bytes into the control
segment of the WQE. It assumes that the linear part contains at least
MLX5E_MIN_INLINE bytes, which can be wrong.

Cited commit verified that driver will not copy more bytes into the
inline header part that the actual size of the packet. Re-factor this
check to make sure we do not exceed the linear part as well.

This fix is aligned with the current driver's assumption that the entire
L2 will be present in the linear part of the SKB.

Fixes: 6aace17e

 ("net/mlx5e: Fix inline header size for small packets")
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>