HID: convert defines of HID class requests into a proper enum

This allows to export the type in BTF and so in the automatically
generated vmlinux.h. It will also add some static checks on the users
when we change the ll driver API (see not below).

Note that we need to also do change in the ll_driver API, but given
that this will have a wider impact outside of this tree, we leave this
as a TODO for the future.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20220902132938.2409206-11-benjamin.tissoires@redhat.com