drm/i915: Do not re-calculate num_rings locally

Since bb8f0f5a ("drm/i915: Split intel_engine allocation
and initialisation") intel_info->num_rings is set early in the
load sequence and so available to be used direclty in the 2nd
load phase.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20170616130339.23015-1-tvrtko.ursulin@linux.intel.com

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2140,7 +2140,7 @@ static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,
 
 		engine->emit_breadcrumb = gen6_sema_emit_breadcrumb;
 
-		num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
+		num_rings = INTEL_INFO(dev_priv)->num_rings - 1;
 		if (INTEL_GEN(dev_priv) >= 8) {
 			engine->emit_breadcrumb_sz += num_rings * 6;
 		} else {
@@ -2184,8 +2184,7 @@ int intel_init_render_ring_buffer(struct intel_engine_cs *engine)
 
 			engine->semaphore.signal = gen8_rcs_signal;
 
-			num_rings =
-				hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
+			num_rings = INTEL_INFO(dev_priv)->num_rings - 1;
 			engine->emit_breadcrumb_sz += num_rings * 8;
 		}
 	} else if (INTEL_GEN(dev_priv) >= 6) {