s390/qeth: drop redundant state checking

Now that qeth always uses dev_close() to shutdown the interface, we can
trust the locking and remove some custom state checks.
qeth_l?_stop_card() is no longer called for a card in UP state, so remove
the checks there too. This basically makes the UP state obsolete, so rip
out the whole thing (except for the sysfs-visible string).

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