score: Add files to Doxygen groups

Update #3707.

cpukit/score/cpu/no_cpu/cpuidle.c

@@ -1,5 +1,14 @@
 /* SPDX-License-Identifier: BSD-2-Clause */
 
+/**
+ * @file
+ *
+ * @ingroup RTEMSScoreCPU
+ *
+ * @brief This source file contains the implementation of the
+ *   _CPU_Thread_Idle_body().
+ */
+
 /*
  * Copyright (C) 2013, 2014 embedded brains GmbH & Co. KG
  *

cpukit/score/cpu/sparc/include/libcpu/grlib-tn-0018.h

@@ -1,5 +1,14 @@
 /* SPDX-License-Identifier: BSD-2-Clause */
 
+/**
+ * @file
+ *
+ * @ingroup RTEMSScoreCPUSPARC
+ *
+ * @brief This header file provides interfaces of the GRLIB-TN-0018 LEON3FT
+ *   RETT Restart Errata fixes.
+ */
+
 /*
  * Copyright (C) 2020 Cobham Gaisler AB
  *

cpukit/score/cpu/sparc/syscall.h

@@ -1 +1,9 @@
+/**
+ * @file
+ *
+ * @ingroup RTEMSScoreCPUSPARC
+ *
+ * @brief This header file provides system call interfaces.
+ */
+
 #define SYS_exit        1