PM / Domains: Ignore domain-idle-states that are not compatible

domain-idle-states property may have phandles to idle state bindings
that may not be compatible with idle state definition defined in [1].
Such phandles would just be ignored and not throw and error when read by
the domain core.

Signed-off-by: Lina Iyer <lina.iyer@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>