[SCSI] zfcp: cleanup use of obsolete strict_strto* functions

strict_strtoul and friends are obsolete. Use kstrtoul functions
instead.

Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>