drm/i915: Clean up g4x+ sprite TILEOFF programming

We defined the bitmasks for DVSTILEOFF but never used them.
Remedy that.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230214134739.25077-3-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>