bsps/leon3: Add missing Doxygen headers

This adds missing Doxygen headers to amba.c and drvmgr_def_drivers.c.

bsps/sparc/leon3/start/amba.c

@@ -1,10 +1,18 @@
 /* SPDX-License-Identifier: BSD-2-Clause */
 
-/*
+/**
+ * @file
+ *
+ * @ingroup RTEMSBSPsSparcLeon3
+ *
+ * @brief This file contains AMBA bus initialization and configuration for LEON3.
+ *
  *  AMBA Plug & Play Bus Driver
  *
  *  This driver hook performs bus scanning.
- *
+ */
+
+/*
  *  COPYRIGHT (c) 2011.
  *  Aeroflex Gaisler
  *

bsps/sparc/leon3/start/drvmgr_def_drivers.c

@@ -1,8 +1,16 @@
 /* SPDX-License-Identifier: BSD-2-Clause */
 
-/*
- *  Default BSP drivers when Driver Manager enabled
+/**
+ * @file
  *
+ * @ingroup RTEMSBSPsSparcLeon3
+ *
+ * @brief This file defines the default driver manager configuration for LEON3.
+ *
+ *  Default BSP drivers when Driver Manager enabled
+ */
+
+/*
  *  COPYRIGHT (c) 2019.
  *  Cobham Gaisler
  *
@@ -45,3 +53,4 @@ drvmgr_drv_reg_func drvmgr_drivers[] __attribute__((weak)) =
 };
 
 #endif
+