perf: Fix IS_ERR() vs NULL check in inherit_event()

The find_get_pmu_context() returns an ERR_PTR() on failure, we should use
IS_ERR() to check the return value.

Fixes: bd27568 ("perf: Rewrite core context handling")
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221114091833.1492575-1-cuigaosheng1@huawei.com

kernel/events/core.c

@@ -13171,7 +13171,7 @@ inherit_event(struct perf_event *parent_event,
 		return child_event;
 
 	pmu_ctx = find_get_pmu_context(child_event->pmu, child_ctx, child_event);
-	if (!pmu_ctx) {
+	if (IS_ERR(pmu_ctx)) {
 		free_event(child_event);
 		return NULL;
 	}