[SCSI] isd200: Allocate sense_buffer for hacked up scsi_cmnd

Since the separation of sense_buffer from scsi_cmnd, Drivers that hack their
own struct scsi_cmnd like here isd200, must also take care of their own
sense_buffer.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>