usb: cdnsp: Fixes issue with Configure Endpoint command

Patch adds flag EP_UNCONFIGURED to detect whether endpoint was
unconfigured. This flag is set in cdnsp_reset_device after Reset Device
command. Among others this command disables all non control endpoints.
Flag is used in cdnsp_gadget_ep_disable to protect controller against
invoking Configure Endpoint command on disabled endpoint. Lack of this
protection in some cases caused that Configure Endpoint command completed
with Context State Error code completion.

Fixes: 3d829045

 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Peter Chen <peter.chen@kernel.org>