mlx4_core: Extend capability flags to 64 bits

The latest firmware adds a second dword containing more device flags,
so extend the device capabilities flags field from 32 to 64 bits.
Derived from patch by Eli Cohen <eli@mellanox.co.il>

Signed-off-by: Or Gerlitz <ogerlitz@mellanox.co.il>
Signed-off-by: Roland Dreier <roland@purestorage.com>