media: radio-keene: fix memory leak in error path

In the Linux kernel, the following vulnerability has been resolved:

media: radio-keene: fix memory leak in error path

Fix a memory leak in usb_keene_probe(). The v4l2 control handler is

initialized and controls are added, but if v4l2_device_register() or

video_register_device() fails afterward, the handler was never freed,

leaking memory.

Add v4l2_ctrl_handler_free() call in the err_v4l2 error path to ensure

the control handler is properly freed for all error paths after it is

initialized.