drive: allow rerror, werror and readonly for if=none

When creating guest disks the qdev way using ...

  -drive if=none,id=$name,args
  -device $driver,drive=$name

it is not possible to specify rerror, werror and readonly arguments
for drive as drive_init allows/blocks them based on the interface (if=)
specified and none isn't white-listed there.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

vl.c

diff --git a/vl.c b/vl.c
index 417554f..7121cd0 100644
--- a/vl.c
+++ b/vl.c
@@ -953,7 +953,7 @@
 
     on_write_error = BLOCK_ERR_STOP_ENOSPC;
     if ((buf = qemu_opt_get(opts, "werror")) != NULL) {
-        if (type != IF_IDE && type != IF_SCSI && type != IF_VIRTIO) {
+        if (type != IF_IDE && type != IF_SCSI && type != IF_VIRTIO && type != IF_NONE) {
             fprintf(stderr, "werror is no supported by this format\n");
             return NULL;
         }
@@ -966,7 +966,7 @@
 
     on_read_error = BLOCK_ERR_REPORT;
     if ((buf = qemu_opt_get(opts, "rerror")) != NULL) {
-        if (type != IF_IDE && type != IF_VIRTIO) {
+        if (type != IF_IDE && type != IF_VIRTIO && type != IF_NONE) {
             fprintf(stderr, "rerror is no supported by this format\n");
             return NULL;
         }
@@ -1114,7 +1114,7 @@
         /* CDROM is fine for any interface, don't check.  */
         ro = 1;
     } else if (ro == 1) {
-        if (type != IF_SCSI && type != IF_VIRTIO && type != IF_FLOPPY) {
+        if (type != IF_SCSI && type != IF_VIRTIO && type != IF_FLOPPY && type != IF_NONE) {
             fprintf(stderr, "qemu: readonly flag not supported for drive with this interface\n");
             return NULL;
         }