nl80211: Get rid of unused assignment warning

The os_snprintf() call here cannot really fail in practice, but since
its result was stored into the local variable and not checked, static
analyzers could warn about the unused assignment. Clean this up by
checking the return value.

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

src/drivers/driver_nl80211.c

@@ -9101,6 +9101,8 @@ static int nl80211_configure_data_frame_filters(void *priv, u32 filter_flags)
 	ret = os_snprintf(path, sizeof(path),
 			  "/proc/sys/net/ipv4/conf/%s/drop_unicast_in_l2_multicast",
 			  bss->ifname);
+	if (os_snprintf_error(sizeof(path), ret))
+		return -1;
 
 	ret = nl80211_write_to_file(path,
 				    !!(filter_flags &