orinoco: avoid assertion in case of NULL pointer

In ezusb_init, if upriv is NULL, the code crashes. However, the caller
in ezusb_probe can handle the error and print the failure message.
The patch replaces the BUG_ON call to error return.
Signed-off-by: Aditya Pakki <pakki001@umn.edu>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/intersil/orinoco/orinoco_usb.c

@@ -1361,7 +1361,8 @@ static int ezusb_init(struct hermes *hw)
 	int retval;
 
 	BUG_ON(in_interrupt());
-	BUG_ON(!upriv);
+	if (!upriv)
+		return -EINVAL;
 
 	upriv->reply_count = 0;
 	/* Write the MAGIC number on the simulated registers to keep