s390/ipl: Fix FCP WWPN and LUN format strings for read

s390/ipl: Fix FCP WWPN and LUN format strings for read

The following git commit changed the behavior of sscanf:

commit 53809751ac230a3611b5cdd375f3389f3207d471
Author: Jan Beulich <JBeulich@suse.com>
Date:   Mon Dec 17 16:01:31 2012 -0800
    sscanf: don't ignore field widths for numeric conversions

This broke the WWPN and LUN sysfs attributes for s390 reipl and dump
on panic.

Example:

$ echo 0x0123456701234567 > /sys/firmware/reipl/fcp/wwpn
$ cat /sys/firmware/reipl/fcp/wwpn
0x0001234567012345

So fix this and use format strings that work also with the
new sscanf implementation:

$ echo 0x012345670123456789 > /sys/firmware/reipl/fcp/wwpn
$ cat /sys/firmware/reipl/fcp/wwpn
0x0123456701234567

Cc: stable@vger.kernel.org # 3.8+
Reviewed-by: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>