vt: keyboard, remove ctrl_alt_del declaration

ctrl_alt_del is already declared in linux/reboot.h which we include. So
remove this second (superfluous) declaration.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20201029113222.32640-1-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>