dt-bindings: mfd: armltd: Move Arm board syscon's to separate schema

dt-bindings: mfd: armltd: Move Arm board syscon's to separate schema

The Arm Ltd board bindings are a bit unusual in that they define child
nodes for various syscon's. The schemas are also incomplete as they lack
constraints on having additional properties and some properties are
missing. As the bindings for the different platforms only vary by
compatibles, combine them into a single schema doc.

Add the "arm,im-pd1-syscon" compatible which was not documented. Add
"ranges", "#address-cells", and "#size-cells properties which were
missing.

With this, fix the error exposed in the register-bit-led binding.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231020142252.3113716-2-robh@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>