common: usb: fix checking condition

We support max USB_MAXENDPOINTS, so need to use
"epno >= USB_MAXENDPOINTS", but not "epno > USB_MAXENDPOINTS".
If use ">", we may exceeds the array of if_desc->ep_desc.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Paul Kocialkowski <contact@paulk.fr>
Cc: "Stefan Brüns" <stefan.bruens@rwth-aachen.de>
Cc: Vincent Palatin <vpalatin@chromium.org>