drm/i915: Fix bits vs. bytes mixup in dbuf block size computation

The spec used to say "8bpp" which someone took to mean 8 bytes per
pixel when in fact it was supposed to be 8 bits per pixel. The
spec has been updated to make it more clear now. Fix the code
to match.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181221171436.8218-4-ville.syrjala@linux.intel.comReviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -4617,7 +4617,7 @@ skl_compute_plane_wm_params(const struct intel_crtc_state *cstate,
 							     intel_pstate);
 
 	if (INTEL_GEN(dev_priv) >= 11 &&
-	    fb->modifier == I915_FORMAT_MOD_Yf_TILED && wp->cpp == 8)
+	    fb->modifier == I915_FORMAT_MOD_Yf_TILED && wp->cpp == 1)
 		wp->dbuf_block_size = 256;
 	else
 		wp->dbuf_block_size = 512;