Use input-device and output-device
Use input-device and output-device

QEMU can now set environment variables from the command line (with -prom-env).
By this means, we can set the output-device and input-device variables,
and SLOF can read it and set stdout and stdin accordingly.

Signed-off-by: Laurent Vivier <240b731be4efaffb85b5d13af681c07e7ef8ddcb@redhat.com>
Tested-by: Nikunj A Dadhania <e2f4a5db9b4735182a88051d1e7a3599f9eac9db@linux.vnet.ibm.com>
Signed-off-by: Alexey Kardashevskiy <ac1fc56530d7d037e1ea666f130daca22d72f964@ozlabs.ru>

qemu/SLOF,qemu/SLOF,qemu/SLOF,stefanberger/SLOF-tpm,aik/SLOF,stefanberger/SLOF-tpm,stefanberger/SLOF-tpm,aik/SLOF,aik/SLOF