virtio: allow finalize_features to fail

This will make it easy for transports to validate features and return
failure.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --cc drivers/lguest/lguest_device.c
Simple merge

diff --cc drivers/misc/mic/card/mic_virtio.c
Simple merge

diff --cc drivers/remoteproc/remoteproc_virtio.c
Simple merge

diff --cc drivers/s390/kvm/kvm_virtio.c
Simple merge

diff --cc drivers/s390/kvm/virtio_ccw.c
Simple merge

diff --cc drivers/virtio/virtio.c
Simple merge

diff --cc drivers/virtio/virtio_mmio.c
Simple merge

diff --cc drivers/virtio/virtio_pci.c
Simple merge

diff --cc include/linux/virtio_config.h
Simple merge