drm/i915: Do not start connector polling on headless sku

Connector polling is waking up the polled device. Polling
is unnecessary if our device is known to not have display.

Fix this and save some power by disabling starting connector
polling when we are having headless sku. Use information from
opregion.

v2: Move headless sku check into INTEL_DISPLAY_ENABLED macro

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220610085429.52935-4-jouni.hogander@intel.com