tty: Remove dead code

-> The ledptrs[] array is never initialized.
-> There is no place where kbd->ledmode is set to LED_SHOW_MEM therefore the if
   statement does not make much sense.
-> Since LED_SHOW_MEM is not used, it can be removed from the header file as well.

Signed-off-by: Andreas Platschek <andi.platschek@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>