staging: kpc2000: use IDA to assign card numbers.

Previously the next card number was assigned from a static int local
variable.  Replaced it with an IDA.  Avoids the assignment of ever-
increasing card-numbers by allowing them to be reused.

Updated TODO.

Corrected format-specifier for unsigned pcard->card_num.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>