amd-xgbe: Use the u32 data type for descriptors

The Tx and Rx descriptors are unsigned 32 bit values.  Use the u32
type, rather than unsigned int, to map these descriptors.

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