amd-xgbe: Remove the XGBE_LINK state bit

The XGBE_LINK bit is used just to determine whether to call the
netif_carrier_on/off functions. Rather than define and use this bit,
just call the functions. The netif_carrier_ok function can be used in
place of checking the XGBE_LINK bit in the future.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>