dt-bindings: arm: ux500: Document missing compatibles

These compatibles are used in Ux500 device trees, but were not documented so
far. Add them to the schema to document them.

Signed-off-by: Stanislav Jakubek <stano.jakubek@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211218144927.GA6388@standask-GA-A55M-S2HP