Buttons are really just values with BitSize == 1, and having a union for
that makes the code more complicated than it needs.

We'll simplify the code a lot using HIDP_VALUE_CAPS everywhere, as the
two structure types are compatible.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>