drm/ci: validate drm/msm XML register files against schema

In order to validate drm/msm register definition files against schema,
reuse the nodebugfs build step. The validation entry is guarded by
the EXPERT Kconfig option and we don't want to enable that option for
all the builds.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240503-fd-fix-lxml-v2-2-f80a60ce21a1@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>