s390/qeth: Fix deadlock in remove_discipline

Problem: qeth_close_dev_handler is a worker that tries to acquire
card->discipline_mutex via drv->set_offline() in ccwgroup_set_offline().
Since commit b41b554c
("s390/qeth: fix locking for discipline setup / removal")
qeth_remove_discipline() is called under card->discipline_mutex and
cancels the work and waits for it to finish.

STOPLAN reception with reason code IPA_RC_VEPA_TO_VEB_TRANSITION is the
only situation that schedules close_dev_work. In that situation scheduling
qeth recovery will also result in an offline interface, when resetting the
isolation mode fails, if the external switch is still set to VEB.
And since commit 0b9902c1 ("s390/qeth: fix deadlock during recovery")
qeth recovery does not aquire card->discipline_mutex anymore.

So we accept the longer pathlength of qeth_schedule_recovery in this
error situation and re-use the existing function.

As a side-benefit this changes the hwtrap to behave like during recovery
instead of like during a user-triggered set_offline.

Fixes: b41b554c

 ("s390/qeth: fix locking for discipline setup / removal")
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Acked-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>