net: ethernet: renesas: ravb_main: test clock rate to avoid division by 0

The clk API may return 0 on clk_get_rate, so we should check the result before
using it as a divisor.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/ravb_main.c

@@ -1691,6 +1691,9 @@ static int ravb_set_gti(struct net_device *ndev)
 	rate = clk_get_rate(clk);
 	clk_put(clk);
 
+	if (!rate)
+		return -EINVAL;
+
 	inc = 1000000000ULL << 20;
 	do_div(inc, rate);