scsi: aacraid: Skip schedule rescan in case of kdump

There is a chance of the driver to be stuck in kdump if drives start
acting up in kdump discovery process and the kernel decides to send eh
resets, which would prompt rescan to be scheduled.

Do not perform a rescan in kdump context, since we do not expect a hotplug
event during kdump and all the devices are going to go away anyway.

Signed-off-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>