drm/i915: Unconfuses QGV vs. PSF point masks

Use separate bitmasks for QGV vs. PSF GV points during
the computation. Makes the whole thing a lot less confusing.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220309164948.10671-8-ville.syrjala@linux.intel.com


Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>