scsi-generic: correct 6-bytes commands transfer length (Laurent Vivier) According to SCSI documentation, for 6 bytes commands (READ(6), WRITE(6)), if transfer length is 0 it specifies 256 blocks. Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5292 c046a42c-6fe2-441c-8c8c-71466251a162