drm/i915: Accept alloc_size == blocks

If the minimum required ddb space for all the planes equals the
total ddb space available we are allowed to use the relevant
watermark level.

Cc: Neel Desai <neel.desai@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190312205844.6339-2-ville.syrjala@linux.intel.comReviewed-by: Matt Roper <matthew.d.roper@intel.com>

drivers/gpu/drm/i915/intel_pm.c

@@ -4378,7 +4378,7 @@ skl_allocate_pipe_ddb(struct intel_crtc_state *cstate,
 			blocks += wm->uv_wm[level].min_ddb_alloc;
 		}
 
-		if (blocks < alloc_size) {
+		if (blocks <= alloc_size) {
 			alloc_size -= blocks;
 			break;
 		}