drm/amd/display: Remove unwanted drm edid references

[WHY]
edid_override and drm_edid_override_connector_update, according to drm
documentation, should not be referred outside drm_edid.

[HOW]
Remove and replace them accordingly. This can tested by IGT's
kms_hdmi_inject test.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>