wacom: SMAP Fixes and Refactoring

Utilize user_memcpy and IS_USER_ADDRESS when necessary to prevent SMAP violations.
Also add a "wacom_device_header" struct to more easily share data between the wacom
kernel driver and input_server addon.

Should fix #14589

Change-Id: Ie2784020b21523f82fd450a2db2de60ccf9d6620
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2783
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>