[SCSI] scsi_dh: Do not use scsilun in rdac hardware handler

RDAC storage controller doesn't seem to use the scsilun format. It uses
only the last byte for LUN.

Signed-off-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>