usb: musb: cppi41: do not call udelay()

according to comment in code, HS completion
will happen pretty fast, instead of using
udelay(), let's just busy loop and drop a
cpu_relax() where udelay() was.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_cppi41.c

@@ -287,7 +287,7 @@ static void cppi41_dma_callback(void *private_data)
 			wait--;
 			if (!wait)
 				break;
-			udelay(1);
+			cpu_relax();
 		} while (1);
 	}
 	list_add_tail(&cppi41_channel->tx_check,