usb: gadget: fotg210-udc: Fix memory leak of fotg210->ep[i]

There is no deallocation of fotg210->ep[i] elements, allocated at
fotg210_udc_probe.

The patch adds deallocation of fotg210->ep array elements and simplifies
error path of fotg210_udc_probe().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Anton Vasilyev <vasilyev@ispras.ru>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>