vt: keyboard, use new API for keyboard_tasklet

vt: keyboard, use new API for keyboard_tasklet

This converts the keyboard_tasklet to use the new API in
commit ad117fab14f5 ("tasklet: Introduce new initialization API")

The new API changes the argument passed to the callback function, but
fortunately the argument isn't used so it is straight forward to use
DECLARE_TASKLET_DISABLED() rather than DECLARE_TASKLET_DISABLED_OLD().

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
Link: https://lore.kernel.org/r/20210127164222.13220-1-kernel@esmil.dk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>