HID: bpf: fix cfi stubs for hid_bpf_ops

With the introduction of commit e42ac141 ("bpf: Check unsupported ops
from the bpf_struct_ops's cfi_stubs"), a HID-BPF struct_ops containing
a .hid_hw_request() or a .hid_hw_output_report() was failing to load
as the cfi stubs were not defined.

Fix that by defining those simple static functions and restore HID-BPF
functionality.

This was detected with the HID selftests suddenly failing on Linus' tree.

Cc: stable@vger.kernel.org # v6.11+
Fixes: 9286675a ("HID: bpf: add HID-BPF hooks for hid_hw_output_report")
Fixes: 8bd0488b ("HID: bpf: add HID-BPF hooks for hid_hw_raw_requests")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>