PM / AVS: SmartReflex: Switch to SPDX Licence ID

Fix up licensing to be inline with Linux conventions.

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>