scsi: fix sign extension problems When assigning a 32-bit value to cmd->xfer (which is 64-bits) it can be erroneously sign extended because the intermediate 32-bit computation is signed. Fix this by standardizing on the ld*_be_p functions. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>