drm/virtio: don't leak bo on drm_gem_object_init failure

drm/virtio: don't leak bo on drm_gem_object_init failure

Reported-by: 李强 <liqiang6-s@360.cn>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170406155941.458-1-kraxel@redhat.com
CVE-2017-10810

(cherry picked from commit 385aee965b4e4c36551c362a334378d2985b722a)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>