The debugfs support for the xpcs registers did not properly use the
specified mmd (xpcs_mmd entry) which resulted in the default mmd
value always being used. Update the debugfs support to generate the
proper mmd register value.
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: David S. Miller <davem@davemloft.net>