Improve #endif comments

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/x509.c b/library/x509.c
index a6335ca..3b53aeb 100644
--- a/library/x509.c
+++ b/library/x509.c
@@ -174,7 +174,7 @@
     }
 }
 
-#endif
+#endif /* !defined(MBEDTLS_X509_REMOVE_INFO) && defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT) */
 
 #if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
 /*