net: cadence: Fix a sleep-in-atomic-context bug in macb_halt_tx()

The kernel module may sleep with holding a spinlock.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] usleep_range
drivers/net/ethernet/cadence/macb_main.c, 648:
	usleep_range in macb_halt_tx
drivers/net/ethernet/cadence/macb_main.c, 730:
	macb_halt_tx in macb_tx_error_task
drivers/net/ethernet/cadence/macb_main.c, 721:
	_raw_spin_lock_irqsave in macb_tx_error_task

To fix this bug, usleep_range() is replaced with udelay().

This bug is found by my static analysis tool DSAC.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/cadence/macb_main.c

@@ -649,7 +649,7 @@ static int macb_halt_tx(struct macb *bp)
 		if (!(status & MACB_BIT(TGO)))
 			return 0;
 
-		usleep_range(10, 250);
+		udelay(250);
 	} while (time_before(halt_time, timeout));
 
 	return -ETIMEDOUT;