net/mlx5: replace external mbuf shared memory

net/mlx5: replace external mbuf shared memory

As an arrangement to the LRO support when a packet can consume all the
stride memory, the external mbuf shared information cannot be anymore
in the end of the stride, because the HW may write the packet data to
all the stride memory.

Move the shared information memory from the stride to the control
memory of the external mbuf.

Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>