[SCSI] ibmvscsi: Non SCSI error status fixup

Some versions of the Virtual I/O Server on Power
return 0x99 in the non-SCSI error status field as success,
rather than 0. This fixes the ibmvscsi driver to treat this
response as success.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>