drm/edid: use the new displayid iterator for tile info

Neatly reduce displayid boilerplate in code. Remove excessive debug
logging while at it, no other functional changes.

The old displayid iterator becomes unused; remove it as well as make
drm_find_displayid_extension() static.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/fa4b5c790b5bdd82063545a6f209f8e9d78a63a7.1617024940.git.jani.nikula@intel.com