dt-bindings: Reference opp-v1 schema in CPU schemas

dt-bindings: Reference opp-v1 schema in CPU schemas

The opp-v1 binding is only used in MIPS and arm32 CPU nodes, so add a
$ref to it in the CPU schemas and drop the "select".

As opp-v1 has long been deprecated, mark it as such.

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20250410-dt-cpu-schema-v2-14-63d7dc9ddd0a@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>