scsi: lpfc: Add shutdown method for kexec

We see lpfc devices regularly fail during kexec. Fix this by adding a
shutdown method which mirrors the remove method.

Cc: <stable@vger.kernel.org>
Signed-off-by: Anton Blanchard <anton@samba.org>
Reviewed-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Tested-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>