drm/i915/selftests: Add some missing error propagation

Add some missing error propagation in live_parallel_switch.

To avoid needlessly burdening the various backport processes, note I am
not marking it as a fix against any patches and not copying stable since
it is debug/selftests only code.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Fixes: 50d16d4 ("drm/i915/selftests: Exercise context switching in parallel")
Fixes: 6407cf5 ("drm/i915/selftests: Stop using kthread_stop()")
Link: https://patchwork.freedesktop.org/patch/msgid/20230605131135.396854-1-tvrtko.ursulin@linux.intel.com

Author: tursulin

drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c

@@ -348,8 +348,10 @@ static int live_parallel_switch(void *arg)
 				continue;
 
 			ce = intel_context_create(data[m].ce[0]->engine);
-			if (IS_ERR(ce))
+			if (IS_ERR(ce)) {
+				err = PTR_ERR(ce);
 				goto out;
+			}
 
 			err = intel_context_pin(ce);
 			if (err) {
@@ -369,8 +371,10 @@ static int live_parallel_switch(void *arg)
 
 		worker = kthread_create_worker(0, "igt/parallel:%s",
 					       data[n].ce[0]->engine->name);
-		if (IS_ERR(worker))
+		if (IS_ERR(worker)) {
+			err = PTR_ERR(worker);
 			goto out;
+		}
 
 		data[n].worker = worker;
 	}
@@ -399,8 +403,10 @@ static int live_parallel_switch(void *arg)
 			}
 		}
 
-		if (igt_live_test_end(&t))
-			err = -EIO;
+		if (igt_live_test_end(&t)) {
+			err = err ?: -EIO;
+			break;
+		}
 	}
 
 out: