remoteproc: avoid registering a virtio device if not supported

Let remoteproc know when the firmware doesn't support any virtio
functionality, so registering a virtio device can be avoided.

This is needed for remote processors that doesn't require any
virtio-based communications, but are still controlled via remoteproc.

[ohad@wizery.com: write commit log]
Signed-off-by: Mark Grosen <mgrosen@ti.com>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

drivers/remoteproc/remoteproc_core.c

@@ -695,7 +695,7 @@ static int
 rproc_handle_virtio_rsc(struct rproc *rproc, struct fw_resource *rsc, int len)
 {
 	struct device *dev = rproc->dev;
-	int ret = 0;
+	int ret = -ENODEV;
 
 	for (; len >= sizeof(*rsc); rsc++, len -= sizeof(*rsc))
 		if (rsc->type == RSC_VIRTIO_DEV) {