drm: ci: Use scripts/config to enable/disable configs

Instead of modifying files in git to enable/disable
configs, use scripts/config on the .config file which
will be used for building the kernel.

Acked-by: Helen Koike <helen.koike@collabora.com>
Suggested-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Vignesh Raman <vignesh.raman@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231207091831.660054-6-vignesh.raman@collabora.com