drm/i915/panel: move panel fixed EDID to struct intel_panel

It's a bit confusing to have two cached EDIDs in struct intel_connector
with slightly different purposes. Make the distinction a bit clearer by
moving the EDID cached for eDP and LVDS panels at connector init time to
struct intel_panel, and name it fixed_edid. That's what it is, a fixed
EDID for the panels.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
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/328350ef918638928a8286cdbab3107c8258332d.1674643465.git.jani.nikula@intel.com