scsi: qla4xxx: Use iscsi_is_session_online()

scsi: qla4xxx: Use iscsi_is_session_online()

__qla4xxx_is_chap_active() just wants to know if a session is online and
does not care about why it's not, so this has it use
iscsi_is_session_online().

This is not a bug now, but the next patch changes the behavior of
iscsi_session_chkready() so this patch just prepares the driver for that
change.

Link: https://lore.kernel.org/r/20210207044608.27585-9-michael.christie@oracle.com
Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>