The udl damage handler is supposed to render 'height' lines, but its
iterator has an obvious typo that makes it miss most lines if the
rectangle does not cover 0/0.

Fix the damage handler to correctly render all lines.

This is a fallout from:

    commit e3758824
    Author: Noralf Trønnes <noralf@tronnes.org>
    Date:   Thu Apr 28 17:18:37 2016 +0200

        drm/udl: Use drm_fb_helper deferred_io support
Tested-by: poma <poma@gmail.com>
Cc: stable@vger.kernel.org # 4.7+
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>