net/mlx4: Aesthetic code changes in multi_func_init

Previous vf_oper and vf_admin code created very long lines, making it hard
to read the code. Added relevant in-struct pointers to reduce code
complexity and avoid code lines spread over 80 lines. Same logic is preserved.

Signed-off-by: Ido Shamay <idos@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>