scsi: zfcp: clean up redundant code with fall through in link down SRB switch case

Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
[maier@linux.vnet.ibm.com: re-worded short description for more details]
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>