ag71xx: fix a memory corruption bug that happens if you flood the interface with packets while it's being brought down fixes boot time crashes under load reported by matteo

SVN-Revision: 22054

target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx_main.c

@@ -454,6 +454,12 @@ static void ag71xx_dma_reset(struct ag71xx *ag)
 	ag71xx_wr(ag, AG71XX_REG_RX_CTRL, 0);
 	ag71xx_wr(ag, AG71XX_REG_TX_CTRL, 0);
 
+	/*
+	 * give the hardware some time to really stop all rx/tx activity
+	 * clearing the descriptors too early causes random memory corruption
+	 */
+	mdelay(1);
+
 	/* clear descriptor addresses */
 	ag71xx_wr(ag, AG71XX_REG_TX_DESC, 0);
 	ag71xx_wr(ag, AG71XX_REG_RX_DESC, 0);