dt-bindings: Add a new binding for Broadcom V3D 3.x and newer GPUs.

These OpenGL ES GPUs are present in the 7268 and 7278 set top box
chips.

v2: no changes
v3: move to gpu/, fix typo

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180430181058.30181-2-eric@anholt.net


Reviewed-by: Rob Herring <robh@kernel.org>