s390/qeth: clean up setting of BLKT defaults

When called from qeth_core_probe_device(), qeth_determine_capabilities()
initializes the device's BLKT defaults. From all other callers, the
ccw_device has already been set online and the BLKT setting is skipped.

Clean this up by extracting the BLKT setting into a separate helper that
gets called from the right place.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>