[SCSI] scsi_dh_rdac: add support for next generation of Dell PV array

This patch is to add DM support for next generation of Dell PowerVault
storage array.

Signed-off-by: Yanqing Liu <Yanqing_Liu@Dell.com>
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>