drm/i915: Implement PSF GV point support

PSF GV points are an additional factor that can limit the
bandwidth available to display, separate from the traditional
QGV points.  Whereas traditional QGV points represent possible
memory clock frequencies, PSF GV points reflect possible
frequencies of the memory fabric.

Switching between PSF GV points has the advantage of incurring
almost no memory access block time and thus does not need to be
accounted for in watermark calculations.

This patch adds support for those on top of regular QGV points.
Those are supposed to be used simultaneously, i.e we are always
at some QGV and some PSF GV point, based on the current video
mode requirements.
Bspec: 64631, 53998

v2: Seems that initial assumption made during ml conversation
    was wrong, PCode rejects any masks containing points beyond
    the ones returned, so even though BSpec says we have around
    8 points theoretically, we can mask/unmask only those which
    are returned, trying to manipulate those beyond causes a
    failure from PCode. So switched back to generating mask
    from 1 - num_qgv_points, where num_qgv_points is the actual
    amount of points, advertised by PCode.

v3: - Extended restricted qgv point mask to 0xf, as we have now
      3:2 bits for PSF GV points(Matt Roper)
    - Replaced val2 with NULL from PCode request, since its not being
      used(Matt Roper)
    - Replaced %d to 0x%x for better readability(thanks for spotting)

Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210531064845.4389-2-stanislav.lisovskiy@intel.com