usb: gadget: s3c-hsotg: Fix invalid free of devm_ allocated data

Since hsotg object is allocated using devm_kzalloc() API, there is no
need to free this explicitly. But we need to keep the release API to
prevent warnings.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>