Input: wacom - correct max Y value on medium bamboos

Medium size Bamboo P&T driver reused max X/Y form older Bamboo 1
medium size tablets and never updated to real value. Actual
active area of tablet is slightly larger in Y direction.

Signed-off-by: Chris Bagwell <chris@cnpbagwell.com>
Acked-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>