qeth: Recognize return codes of ccw_device_set_online

Setting a qeth device online requires to call function
ccw_device_set_online() for read-, write-, and data-subchannel.
Failures should be detected immediately without an attempt to
invoke follow-on activity qeth_qdio_clear_card().,

In addition, ccw_device_set_online calls are consolidated in
qeth_core_main.c only.

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>