megaraid_sas: reduce memory footprints in kdump mode

This patch will reduce memory footprints of megaraid_sas driver when
booted in kdump mode.  Driver will not allocate memory for optional and
perfromance oriented features.  Below are key changes done in
megaraid_sas driver to do this:

1. Limit Controller's queue depth to 100 in kdump mode.

2. Do not allocate memory for system info buffer and PD info buffer.

3. Disable performance oriented features e.g. Disable RDPQ mode, disable
   dual queue depth, restrict to single MSI-x vector.

Signed-off-by: Sumit Saxena <sumit.saxena@broadcom.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>