drm/i915/bios: move ddc pin mapping code next to ddc pin sanitize

Move code around to avoid a forward declaration in the future.

Cc: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/8c5f723e0b2d8ffd6f47068edf710947b45843be.1630512523.git.jani.nikula@intel.com