net/mlx5: prefix all functions with mlx5

net/mlx5: prefix all functions with mlx5

This change removes the need to distinguish unlocked priv_*() functions
which are therefore renamed using a mlx5_*() prefix for consistency.

At the same time, all functions from mlx5 uses a pointer to the ETH device
instead of the one to the PMD private data.

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>