drm/i915: hide VLV PUNIT IOSF sideband qos handling better

The sideband latency qos request is only used for VLV PUNIT
access. Abstract it better, and also add the request for VLV only.

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/92632f64c1256bfafe7ebf49c1ad0618157d9484.1730193891.git.jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>