s390/cio: cio_ignore_proc_seq_next should increase position index

s390/cio: cio_ignore_proc_seq_next should increase position index

[ Upstream commit 8b101a5e14f2161869636ff9cb4907b7749dc0c2 ]

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283
Link: https://lore.kernel.org/r/d44c53a7-9bc1-15c7-6d4a-0c10cb9dffce@virtuozzo.com
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>