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 <[email protected]>

headers/private/input/wacom_driver.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2020, Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the MIT license.
+ */
+#ifndef WACOM_DRIVER_H
+#define WACOM_DRIVER_H
+
+
+#include <SupportDefs.h>
+
+
+typedef struct {
+	uint16	vendor_id;
+	uint16	product_id;
+	size_t	max_packet_size;
+} _PACKED wacom_device_header;
+
+
+#endif // WACOM_DRIVER_H