can: etas_es58x: allow partial RX URB allocation to succeed

When es58x_alloc_rx_urbs() fails to allocate the requested number of
URBs but succeeds in allocating some, it returns an error code.
This causes es58x_open() to return early, skipping the cleanup label
'free_urbs', which leads to the anchored URBs being leaked.

As pointed out by maintainer Vincent Mailhol, the driver is designed
to handle partial URB allocation gracefully. Therefore, partial
allocation should not be treated as a fatal error.

Modify es58x_alloc_rx_urbs() to return 0 if at least one URB has been
allocated, restoring the intended behavior and preventing the leak
in es58x_open().

Fixes: 8537257874e9 ("can: etas_es58x: add core support for ETAS ES58X CAN USB interfaces")
Reported-by: [e-mail]
Closes: https://syzkaller.appspot.com/bug?extid=e8cb6691a7cf68256cb8
Signed-off-by: Szymon Wilczek <[e-mail]>
Reviewed-by: Vincent Mailhol <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

drivers/net/can/usb/etas_es58x/es58x_core.c

···
 	dev_dbg(dev, "%s: Allocated %d rx URBs each of size %u\n",
 		__func__, i, rx_buf_len);
 
-	return ret;
+	return 0;
 }
 
 /**