[SCSI] pmcraid: add support for set timestamp command and other fixes

The following are the fixes in this patch:

1. Added support of set timestamp command in the driver
2. Pass all status code to mgmt application. Earlier we were passing
   only failed ones.
3. Call class_destroy after unregister_chrdev and pci_unregister_driver

Signed-off-by: Anil Ravindranath <anil_ravindranath@pmc-sierra.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>