ravb: Add magic_pkt to struct ravb_hw_info

E-MAC on R-Car supports magic packet detection, whereas RZ/G2L
does not support this feature. Add magic_pkt to struct ravb_hw_info
and enable this feature only for R-Car.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>