cxgb4vf: Fix off-by-one error checking for the end of the mailbox delay array

Fix off-by-one error in checking for the end of the mailbox response delay
array.  We ended up walking off the end and, if we were unlucky, we'd end up
pulling in a 0 and never terminate the mailbox response delay loop ...
Signed-off-by: Casey Leedom <leedom@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/cxgb4vf/t4vf_hw.c

@@ -163,7 +163,7 @@ int t4vf_wr_mbox_core(struct adapter *adapter, const void *cmd, int size,
 	for (i = 0; i < 500; i += ms) {
 		if (sleep_ok) {
 			ms = delay[delay_idx];
-			if (delay_idx < ARRAY_SIZE(delay))
+			if (delay_idx < ARRAY_SIZE(delay) - 1)
 				delay_idx++;
 			msleep(ms);
 		} else