Staging: vt6655-6: potential info leak in private_ioctl()

Smatch has a new check for Rosenberg type information leaks where
structs are copied to the user with uninitialized stack data in them.

In this path, the .uLinkRate member doesn't get initialized so I've
set it to zero.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>