HID: wacom: Unify speed setting

This patch unifies speed setting for both supported tablets. Functionality
of "wacom_poke" (used only by Graphire) is now in "wacom_set_features".
Reporting speed for both tablets can be changed by somethinkg like:

echo 1 > /sys/class/bluetooth/hci0/hci0:1/{device No}/speed

Accepted values:
0 - low speed,
1 - high speed.

The way of changing reporting speed is the same for Graphire and Intuos4 WL.

Signed-off-by: Przemo Firszt <przemo@firszt.eu>
Acked-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>