drm/virtio: Add spaces around operators

This patch fixes the checkpatch.pl check:

virtgpu_ioctl.c:535: CHECK: spaces preferred around that '|' (ctx:VxV)
virtgpu_vq.c:277: CHECK: spaces preferred around that '+' (ctx:VxV)
...

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/8402b55696b44483ba2e1f6aaeb53bf709ffbfe7.1519343668.git.rodrigosiqueiramelo@gmail.com


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