amd-xgbe: Properly handle feature changes via ethtool

The ndo_set_features callback function was improperly using an unsigned
int to save the current feature value for features such as NETIF_F_RXCSUM.
Since that feature is in the upper 32 bits of a 64 bit variable the
result was always 0 making it not possible to actually turn off the
hardware RX checksum support.  Change the unsigned int type to the
netdev_features_t type in order to properly capture the current value
and perform the proper operation.

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