debug: mipi_stp_decoder: move to os_services doxygen group

The API was placed under a non-existing group: coresight_apis. Place it
under os_services, as other debug/ APIs.

Signed-off-by: Gerard Marull-Paretas <[email protected]>

Author: gmarull

include/zephyr/debug/mipi_stp_decoder.h

@@ -15,7 +15,7 @@ extern "C" {
 
 /**
  * @defgroup mipi_stp_decoder_apis STP Decoder API
- * @ingroup coresight_apis
+ * @ingroup os_services
  * @{
  */