tty: rocket: Remove RCPK_GET_STRUCT ioctl

If the cmd is RCPK_GET_STRUCT, copy_to_user will copy
info to user space. As info->port.ops is the address of
a constant object rocket_port_ops (assigned in init_r_port),
a kernel address leakage happens.

Remove the RCPK_GET_STRUCT ioctl.

Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>