s390/cio: remove unused ccw_device_force_console() declaration

ccw_device_force_console() has been removed by
commit 8cc0dcfd ("s390/cio: remove pm support from
ccw bus driver"), so remove the declaration, too.

Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Acked-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>