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 <[e-mail]>
Acked-by: Helen Koike <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/ci/build.sh

···
 apt-get update
 apt-get install -y libssl-dev
 
+# for msm header validation
+apt-get install -y python3-lxml
+
 if [[ "$KERNEL_ARCH" = "arm64" ]]; then
     GCC_ARCH="aarch64-linux-gnu"
     DEBIAN_ARCH="arm64"

drivers/gpu/drm/ci/build.yml

···
   extends: .build:arm64
   variables:
     DISABLE_KCONFIGS: "DEBUG_FS"
+    ENABLE_KCONFIGS: "EXPERT DRM_MSM_VALIDATE_XML"
 
 build:x86_64:
   extends: .build:x86_64