UPSTREAM: drm/virtio: fix a wait_event condition

outcnt may be greater than 1 since commit e1218b8c0cc1 ("drm/virtio:
Use vmalloc for command buffer allocations.").

Bug: 254441685
Fixes: e1218b8c0cc1 ("drm/virtio: Use vmalloc for command buffer allocations.")
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Cc: David Riley <davidriley@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20200205181955.202485-2-olvaffe@gmail.com


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 58547d7d5c6f4c5d18a1719c87799d825741e64a)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I2ffff167b66589dfd5655a495c927d2ec92eaeb1