drm/i915/dmc: hide DMC version macros

The macros are now only needed within intel_dmc.c, so move them there.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220330113417.220964-2-jani.nikula@intel.com