drm/virtio: kconfig: Fixup white space.

Use tabs instead of spaces.
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1475913318-12275-1-git-send-email-peter.griffin@linaro.org
Link: http://patchwork.freedesktop.org/patch/msgid/1476238699-25820-1-git-send-email-jiang.biao2@zte.com.cn