s390: remove use of seq_printf return value

s390: remove use of seq_printf return value

The seq_printf return value, because it's frequently misused,
will eventually be converted to void.

See: commit 1f33c41c03da ("seq_file: Rename seq_overflow() to
     seq_has_overflowed() and make public")

Signed-off-by: Joe Perches <[email protected]>
Acked-by: Sebastian Ott <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Peter Oberparleiter <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>