[S390] tty3270: fix put_char fail/success conversion.

The wrong function got coverted ;)

  CC      drivers/s390/char/tty3270.o
drivers/s390/char/tty3270.c:1747:
 warning: initialization from incompatible pointer type

Acked-by: Alan Cox <alan@redhat.com>
Cc: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>