Remove error_description variable from strerr functions

This was suggested on this PR: https://github.com/ARMmbed/mbedtls/pull/3176

Signed-off-by: Gaurav Aggarwal <aggarg@amazon.com>
diff --git a/scripts/generate_errors.pl b/scripts/generate_errors.pl
index cb59669..5aef37a 100755
--- a/scripts/generate_errors.pl
+++ b/scripts/generate_errors.pl
@@ -161,8 +161,7 @@
     }
 
     ${$code_check} .= "${white_space}case -($error_name):\n".
-                      "${white_space}    error_description = \"$module_name - $description\";\n".
-                      "${white_space}    break;\n"
+                      "${white_space}    return \"$module_name - $description\";\n"
 };
 
 if ($ll_old_define ne "")