usb: cdns3: Fix runtime PM imbalance on error

pm_runtime_get_sync() increments the runtime PM usage counter even
when it returns an error code. Thus a pairing decrement is needed on
the error handling path to keep the counter balanced.

Reviewed-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Felipe Balbi <balbi@kernel.org>