dt-bindings: display: remove zte,vou.txt binding doc

The zte zx platform was removed in commit 89d4f98 ("ARM: remove zte
zx platform") and the zxdrm driver is going to be removed in v5.15 via
drm tree. Let's remove the now obsolete binding doc.

Cc: Arnd Bergmann <[email protected]>
Cc: Jun Nie <[email protected]>
Cc: Shawn Guo <[email protected]>
Signed-off-by: Zenghui Yu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Rob Herring <[email protected]>

Author: Zenghui Yu