qeth: HiperSockets mcl string conversion (pre z9 mach)

The pre z9 machines provide an mcl string in EBCDIC format,
z9 or later provide string in ASCII format.

Signed-off-by: Klaus-Dieter Wacker <kdwacker@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>