drm/i915/sdvo: stop caching has_hdmi_audio in struct intel_sdvo

Use the information stored in display info.

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1e02f2f7381dfcee6e4160a5fc17aea6ff04baf9.1685437500.git.jani.nikula@intel.com