Input: wacom - add 3 new models - 6A, 6B, and 97

Tested-by: Alex Tervoort <alex.tervoort@gmail.com> for 6A
Signed-off-by: David Foley <favux.is@gmail.com>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>