scsi: lpfc: Fix return value of board_mode store routine in case of online failure

On hbacmd reset failure, observing wrong string "nline" in kernel log.

On failure, non negative value (1) is returned from sysfs store
routine. It is interpreted as count by kernel and store routine is
called again with the remaining characters as input.

Fix: Return negative error code (-EIO) in case of failure.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <james.smart@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>