CVE-2026-63916: HID: wacom: Fix OOB write in wacom_hid_set_device_mode()

In the Linux kernel, the following vulnerability has been resolved:

HID: wacom: Fix OOB write in wacomhidsetdevicemode()

wacomhidsetdevicemode() currently assumes that the HIDDGINPUTMODE usage is always located in the first field (field[0]) of the feature report. However, a device can specify HIDDGINPUTMODE in a different field.

If HIDDGINPUTMODE is in a field other than the first one and the first field has a reportcount smaller than the usageindex of HIDDGINPUTMODE, this leads to an out-of-bounds write to r->field[0]->value.

Fix this by storing the field index of HIDDGINPUTMODE in 'struct hiddata' during feature mapping. In wacomhidsetdevicemode(), use this stored field index to access the correct field and add bounds checks to ensure both the field index and the value index are within valid ranges before writing.