kobject: free memory if netlink_kernel_create() fails

There is a kfree(ue_sk) missing on the error path if
netlink_kernel_create() fails.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>