drm/edid: convert drm_edid_iter_begin() to drm_edid

We'll need to propagate drm_edid everywhere.

v2: Rebase

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/24dfb5fd9026ebef573bb55b368b94e56cae5cec.1652097712.git.jani.nikula@intel.com