linux/build.sh: re-enable copying pocket reform dts (disabled in 'initial support for meson-g12b-bananapi-cm4-mnt-reform2')

.gitlab-ci.yml: install debian-archive-keyring because symlink chdist/base/etc/apt/trusted.gpg.d/debian-archive-keyring.gpg points to it

linux/patches/imx8mq-mnt-reform2/0005-imx8mq-import-HDMI-driver-and-make-DCSS-compatible-w.patch: move cdn-mhdp stuff into cdns subdirectory

split build job into parallel jobs

See merge request !8

Revert ".gitlab-ci.yml: sbuild-createchroot --include=adduser to prevent adduser from being removed after the build (which will fail as it's now Protected:yes)"

This reverts commit 2e1d3657.

This reverts commit 13a7ab05.

linux/patches/0005-imx8mq-import-HDMI-driver-and-make-DCSS-compatible-w.patch: let DRM_CDNS_HDMI select DRM_DISPLAY_HDMI_HELPER

.gitlab-ci.yml: sbuild-createchroot --include=adduser to prevent adduser from being removed after the build (which will fail as it's now Protected:yes)

reform2-hdmi.dts: add ecspi entry for lpc and use chip name in device id

See merge request !5

This reverts commit a3f7df22.