scsi: Fix cdrom boot crash when no medium present
scsi: Fix cdrom boot crash when no medium present

Signed-off-by: Nikunj A Dadhania <e2f4a5db9b4735182a88051d1e7a3599f9eac9db@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <a7089bb6e7e92505d88aaff006cbdd60cc9120b6@kernel.crashing.org>

open-power-host-os/slof,leilihh/SLOF,aik/SLOF,stefanberger/SLOF-tpm,aik/SLOF,mdroth/SLOF,leilihh/SLOF,dgibson/SLOF,aik/SLOF,open-power-host-os/slof,mdroth/SLOF,k0da/SLOF,open-power-host-os/slof,qemu/SLOF,mdroth/SLOF,agraf/SLOF,k0da/SLOF,stefanberger/SLOF-tpm,leilihh/SLOF,agraf/SLOF,dgibson/SLOF,agraf/SLOF,open-power-host-os/slof,dgibson/SLOF,leilihh/SLOF,k0da/SLOF,stefanberger/SLOF-tpm,dgibson/SLOF,qemu/SLOF,agraf/SLOF,qemu/SLOF,mdroth/SLOF,k0da/SLOF