NTB: fix possible name leak in ntb_register_device()

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

NTB: fix possible name leak in ntb_register_device()

If device_register() fails in ntb_register_device(), the device name

allocated by dev_set_name() should be freed. As per the comment in

device_register(), callers should use put_device() to give up the

reference in the error path. So fix this by calling put_device() in the

error path so that the name can be freed in kobject_cleanup().

As a result of this, put_device() in the error path of

ntb_register_device() is removed and the actual error is returned.

[mani: reworded commit message]