s390/qeth: use QUERY OAT for initial link info

Improve the initial link info with data obtained from QUERY OAT.
Doing so _only_ at initialization time avoids
1. dealing with multi-part replies, and
2. sifting through all the data that may get returned at runtime.

This allows us to determine the correct port type for the 1000BT variant
of recent OSA adapter generations (where the .card_type field in
QUERY CARD INFO is no longer sufficient).

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