HID: bpf: add a driver for the Huion Inspiroy 2S (H641P)

This is a a driver for the Huion Inspiroy 2S in both modes (firmware mode
and tablet mode). This device has 6 buttons and a wheel, all of which
send key combinations (see the comments for the defaults). Luckily the
device is quite limited in that it only supports one button down at a
time, so with this BPF we can simply remap the 8 possible report IDs to
our own custom-built report descriptor.

If the device is in tablet mode (e.g. using huion-switcher it sends
everything through the vendor report instead). This BPF program converts
both, depending which devices you attach to you get both. Or if you
attach to all hid devices you get a duplicate device but it'll work
either way.

This BPF should be mostly compatible for the M and L as well though they
have more buttons so the rdescs will need some minor rework.

Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/85
Link: https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/109Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Link: https://patch.msgid.link/20240627-import-bpf-v1-2-0dbcda4a5b1f@kernel.orgSigned-off-by: Benjamin Tissoires <bentiss@kernel.org>