Check os_snprintf() result more consistently - success case

This converts os_snprintf() result validation cases to use
os_snprintf_error() in cases where success condition was used to execute
a step. These changes were done automatically with spatch using the
following semantic patch:

@@
expression E1,E2,E3;
statement S1;
@@

  E1 = os_snprintf(E2, E3, ...);
- if (\( E1 >= 0 \| E1 > 0 \) && \( (size_t) E1 < E3 \| E1 < (int) E3 \| E1 < E3 \))
+ if (!os_snprintf_error(E3, E1))
  S1

Signed-off-by: Jouni Malinen <j@w1.fi>

src/eap_server/eap_server_ttls.c

@@ -409,7 +409,7 @@ static struct wpabuf * eap_ttls_build_phase2_mschapv2(
 				       RADIUS_VENDOR_ID_MICROSOFT, 1, 43);
 		*pos++ = data->mschapv2_ident;
 		ret = os_snprintf((char *) pos, end - pos, "S=");
-		if (ret >= 0 && ret < end - pos)
+		if (!os_snprintf_error(end - pos, ret))
 			pos += ret;
 		pos += wpa_snprintf_hex_uppercase(
 			(char *) pos, end - pos, data->mschapv2_auth_response,