qeth: show new mac-address if its setting fails

Setting of a MAC-address may fail because an already used MAC-address
is to bet set or because of authorization problems. In those cases
qeth issues a message, but the mentioned MAC-address is not the
new MAC-address to be set, but the actual MAC-address. This patch
chooses now the new MAC-address to be set for the error messages.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>