dt-bindings: display: simple: add Tianma TM070JVHG33

Add the Tianma Micro-electronics TM070JVHG33 7.0" WXGA display to the
panel-simple compatible list.

Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200612072219.13669-3-matthias.schiffer@ew.tq-group.com