drm/i915/dg2: Correct DSS check for Wa_1308578152

When converting our DSS masks to bitmaps, we fumbled the condition used
to check whether any DSS are present in the first gslice.  Since
intel_sseu_find_first_xehp_dss() returns a 0-based number, we need a >=
condition rather than >.

Fixes: b87d3901 ("drm/i915/sseu: Disassociate internal subslice mask representation from uapi")
Reported-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220607154724.3155521-1-matthew.d.roper@intel.com