There are a few MAC/PHYs combinations which now support > 1Gbps. These
may need to make use of link modes with bits > 31. Thus their
supported PHY features or advertised features cannot be implemented
using the current bitmap in a u32. Convert to using a linkmode bitmap,
which can support all the currently devices link modes, and is future
proof as more modes are added.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>