s390/debug: use pK for kernel pointers

the s390 debug feature (/sys/kernel/debug/s390dbf/) shows the kernel
pointer of the calling function even for kptr_restrict == 2. Let us
use pK instead of p.

This hides the kernel addresses for kptr_restrict == 2:

root@host $ echo 2 >  /proc/sys/kernel/kptr_restrict
root@host $ tail -n1  /sys/kernel/debug/s390dbf/cio_msg/sprintf
00 01511461280:386645 2 - 00 0000000000000000  snsid: device 0.0.3f68: rc=0 3990/e9 3390/0c

root@host $ echo 1 >  /proc/sys/kernel/kptr_restrict
root@host $ tail -n1  /sys/kernel/debug/s390dbf/cio_msg/sprintf
00 01511461280:386645 2 - 00 000000000071171c  snsid: device 0.0.3f68: rc=0 3990/e9 3390/0c

root@host $ echo 0 >  /proc/sys/kernel/kptr_restrict
root@host $ tail -n1  /sys/kernel/debug/s390dbf/cio_msg/sprintf
00 01511461280:386645 2 - 00 000000000071171c  snsid: device 0.0.3f68: rc=0 3990/e9 3390/0c

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>