Input: wacom - add IDs for two new Bamboo PTs

Add two new Bamboo Pen & Touch models:

Bamboo Comic Medium			(CTH661/S1; Product ID = 0xd8)
Bamboo P & T Special Edition Small	(CTH461/L;  Product ID = 0xdA)

Tested-by: IRIE Shinsuke <irieshinsuke@yahoo.co.jp>
Tested-by: Andrea Cadeddu <mrernia@gmail.com>
Signed-off-by: David Foley <favux.is@gmail.com>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>