drm/virtio: Remove restriction of non-zero blob_flags

With native userspace drivers in guest, a lot of GEM objects need to be
neither shared nor mappable.  And in fact making everything mappable
and/or sharable results in unreasonably high fd usage in host VMM.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220219170301.545432-1-robdclark@gmail.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_ioctl.c

@@ -609,8 +609,7 @@ static int verify_blob(struct virtio_gpu_device *vgdev,
 	if (!vgdev->has_resource_blob)
 		return -EINVAL;
 
-	if ((rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK) ||
-	    !rc_blob->blob_flags)
+	if (rc_blob->blob_flags & ~VIRTGPU_BLOB_FLAG_USE_MASK)
 		return -EINVAL;
 
 	if (rc_blob->blob_flags & VIRTGPU_BLOB_FLAG_USE_CROSS_DEVICE) {