qeth: remove extraneous length from %pM format

Length specifier in the %pM format is not supported (at least, not
documented). Remove it, and also an extraneous '&' for the array.

Signed-off-by: Eugene Crosser <Eugene.Crosser@ru.ibm.com>
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>