drm/i915/sdvo: ignore returned broken edid on intel_sdvo_tmds_sink_detect

If drm_edid_raw returned NULL on error don't try accessing anything behind
that NULL

Signed-off-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230803143530.27601-1-juhapekka.heikkila@gmail.com