usb: Fix usb_ep_find_packet_by_id

usb_ep_find_packet_by_id mistakenly only checks the first packet and if that
is not a match, keeps trying the first packet! This patch fixes this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
