PM / QoS: Restore DEV_PM_QOS_MIN/MAX_FREQUENCY

Support for adding per-device frequency limits was removed in
commit 2aac8bdf ("PM: QoS: Drop frequency QoS types from device PM QoS")
after cpufreq switched to use a new "freq_constraints" construct.

Restore support for per-device freq limits but base this upon
freq_constraints. This is primarily meant to be used by the devfreq
subsystem.

This removes the "static" marking on freq_qos_apply but does not export
it for modules.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Tested-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>