drm/i915/selftests: Initialise err in case there are no engines!

drivers/gpu/drm/i915//gt/selftest_engine_heartbeat.c:255 live_heartbeat_fast() error: uninitialized symbol 'err'.
drivers/gpu/drm/i915//gt/selftest_engine_heartbeat.c:320 live_heartbeat_off() error: uninitialized symbol 'err'.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191025135943.12524-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/selftest_engine_heartbeat.c

@@ -240,7 +240,7 @@ static int live_heartbeat_fast(void *arg)
 	struct intel_gt *gt = arg;
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
-	int err;
+	int err = 0;
 
 	/* Check that the heartbeat ticks at the desired rate. */
 	if (!CONFIG_DRM_I915_HEARTBEAT_INTERVAL)
@@ -302,7 +302,7 @@ static int live_heartbeat_off(void *arg)
 	struct intel_gt *gt = arg;
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
-	int err;
+	int err = 0;
 
 	/* Check that we can turn off heartbeat and not interrupt VIP */
 	if (!CONFIG_DRM_I915_HEARTBEAT_INTERVAL)