Add missing asterisk to doxygen closures

Clarify section names next to closing braces
Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/include/mbedtls/pem.h b/include/mbedtls/pem.h
index baceb07..a2b73f8 100644
--- a/include/mbedtls/pem.h
+++ b/include/mbedtls/pem.h
@@ -51,7 +51,7 @@
 #define MBEDTLS_ERR_PEM_FEATURE_UNAVAILABLE               -0x1400
 /** Bad input parameters to function. */
 #define MBEDTLS_ERR_PEM_BAD_INPUT_DATA                    -0x1480
-/* \} name */
+/** \} name PEM Error codes */
 
 #ifdef __cplusplus
 extern "C" {