amd-xgbe: Support for 64-bit management counter registers

Add support for reading all management counter registers as 64-bit
values.  The indication of whether to read the high 32-bits to form
a 64-bit value is indicated in the version data.

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