usb: rework usb_maxpacket() using usb_pipe_endpoint()

Rework the body of usb_maxpacket() and just rely on the
usb_pipe_endpoint() helper function to retrieve the host endpoint
instead of doing it by hand.
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/r/20220317035514.6378-10-mailhol.vincent@wanadoo.frSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/usb.h

@@ -1971,13 +1971,7 @@ usb_pipe_endpoint(struct usb_device *dev, unsigned int pipe)
 
 static inline u16 usb_maxpacket(struct usb_device *udev, int pipe)
 {
-	struct usb_host_endpoint	*ep;
-	unsigned			epnum = usb_pipeendpoint(pipe);
-
-	if (usb_pipeout(pipe))
-		ep = udev->ep_out[epnum];
-	else
-		ep = udev->ep_in[epnum];
+	struct usb_host_endpoint *ep = usb_pipe_endpoint(udev, pipe);
 
 	if (!ep)
 		return 0;