HID: bpf: convert in-tree fixes into struct_ops

Very mechanical:
- Change HID_BPF_DEVICE_EVENT and HID_BPF_RDESC_FIXUP #defines
- add a matching SEC(".struct_ops.link")
- in ArtistPro16Gen2 make the 2 functions static and have a new one
  calling them

Link: https://lore.kernel.org/r/20240608-hid_bpf_struct_ops-v3-7-6ac6ade58329@kernel.org


Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>