drm/i915/selftests: Fix an error handling path in 'mock_gem_device()'

Goto the right label in case of error, otherwise there is a leak.
This has been introduced by c5cf9a9147ff. In this patch a goto has not been
updated.

Fixes: c5cf9a9147ff ("drm/i915: Create a kmem_cache to allocate struct i915_priolist from")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://patchwork.freedesktop.org/patch/msgid/20170719223503.30580-1-christophe.jaillet@wanadoo.fr
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/selftests/mock_gem_device.c

@@ -228,7 +228,7 @@ struct drm_i915_private *mock_gem_device(void)
 	mkwrite_device_info(i915)->ring_mask = BIT(0);
 	i915->engine[RCS] = mock_engine(i915, "mock");
 	if (!i915->engine[RCS])
-		goto err_dependencies;
+		goto err_priorities;
 
 	i915->kernel_context = mock_context(i915, NULL);
 	if (!i915->kernel_context)