dt-bindings: gpio: Create a trivial GPIO schema

Many simple GPIO controllers without interrupt capability have the same
schema other than their compatible value. Combine all these bindings
into a single schema. The criteria to be included here is must use 2
cells, have no interrupt capability, have 0 or 1 "reg" entries, and
have no other resources (like clocks).

Note that "ngpios" is now allowed in some cases it wasn't before and
constraints on it have been dropped.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250714201959.2983482-1-robh@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: robherring