tg3: Extend loopback test timeout

This patch extends the loopback test timeout from 250 usec to 350 usec.
When the 5785 is paired against an AC131 phy, the older timeout is
just a little too close to the expected performance based on timings.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/tg3.c

@@ -10424,8 +10424,8 @@ static int tg3_run_loopback(struct tg3 *tp, int loopback_mode)
 
 	udelay(10);
 
-	/* 250 usec to allow enough time on some 10/100 Mbps devices.  */
-	for (i = 0; i < 25; i++) {
+	/* 350 usec to allow enough time on some 10/100 Mbps devices.  */
+	for (i = 0; i < 35; i++) {
 		tw32_f(HOSTCC_MODE, tp->coalesce_mode | HOSTCC_MODE_ENABLE |
 		       coal_now);