s390/qeth: remove HARDSETUP state

qeth_l?_stop_card() is _never_ called while in HARDSETUP state, and
there's no other usage of the card state that relies on the
DOWN -> HARDSETUP -> SOFTSETUP transition.

As related cleanup, remove the check in qeth_realloc_buffer_pool() as it
is already done by the callers.

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