dt-bindings: vendor-prefixes: Add prefix for Miyoo

Add a prefix for "miyoo". The only details I can find about
the company is their aliexpress store "miyoo global store":
https://www.aliexpress.com/store/912663639



Signed-off-by: Daniel Palmer <daniel@0x0f.com>
Acked-by: Rob Herring <robh@kernel.org>