[SCSI] megaraid_sas: Add driver workaround for PERC5/1068 kdump kernel panic

The following patch for megaraid_sas adds a driver workaround for
PERC5/1068 based controller FW that keeps a command from the main
kernel that the driver cannot cancel which was causing a kernel panic
in shutdown of the kdump kernel.

Signed-off-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>