doxygen: score: adjust doc in mppkt.h to doxygen guidelines

Update #3706.

cpukit/include/rtems/score/mppkt.h

@@ -1,6 +1,8 @@
 /**
  * @file
  *
+ * @ingroup RTEMSScoreMPPacket
+ *
  * @brief Specification for the Packet Handler
  *
  * This package is the specification for the Packet Handler.
@@ -35,11 +37,14 @@ extern "C" {
  *
  * @ingroup RTEMSScore
  *
+ * @brief MP Packte Handler
+ *
  * This handler encapsulates the primary definition of MPCI packets.  This
  * handler defines the part of the packet that is common to all remote
  * operations.
+ *
+ * @{
  */
-/**@{*/
 
 /**
  *  The following enumerated type defines the packet classes.