dt-bindings: arm: sunxi: Add H5 MBUS compatible

The H5 SoC has a MBUS very similar to the H3 SoC, but it has a smaller
MDFS divider range (1-4 instead of 1-16). Add a separate compatible for
this variant.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20211118031841.42315-4-samuel@sholland.org