scsi: qla2xxx: Fix fw dump corruption

If fw dump buffer size changes and there is an existing fw dump, then save
the old dump in the newly allocated buffer.

Signed-off-by: Quinn Tran <quinn.tran@cavium.com>
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>