s390/qeth: tolerate error when querying card info

By the time that our .get_link_ksettings() code issues a QUERY CARD INFO
cmd to get link-related information, we already set up a good amount of
static link data.

Return this data when the cmd fails, same as when the cmd is not
supported.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>