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.fr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>