Since commit 5acf4911 ("drm/msm: import gen_header.py script from Mesa"),
compilation is broken on machines having python versions older than 3.9
due to dependency on argparse.BooleanOptionalAction.

Switch to use simple bool for the validate flag to remove the dependency.

Fixes: 5acf4911 ("drm/msm: import gen_header.py script from Mesa")
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240507230440.3384949-1-quic_abhinavk@quicinc.com