Staging: lustre: error handling tweaks in obd_ioctl_getdata()

1)  The places which called copy_from_user() were returning the number
of bytes not copied instead of -EFAULT.

2) The user could trigger a memory leak if the condition
"(hdr.ioc_len != data->ioc_len)" was true.  Instead of adding a new call
to OBD_FREE_LARGE(), I created a free_buf label and changed everything
to use that label.

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