scsi: zfcp: Clean up sysfs code for SFP diagnostics

scsi: zfcp: Clean up sysfs code for SFP diagnostics

The error path from zfcp_adapter_enqueue() no longer attempts to remove the
diagnostics attributes if they haven't been created yet.

So remove the manual 'sysfs_established' guard for this case, and use
device_add_groups() to add all adapter-related sysfs attributes in one go.

Link: https://lore.kernel.org/r/37a97537f675d643006271f37723c346189b6eec.1618417667.git.bblock@linux.ibm.com
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>