perf/core: Remove some dead code

perf_init_event() can't return NULL.  If it did, the error handling is
incomplete and we would crash.  I have removed this confusing dead code.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/20170522090348.5g7yyld5en3yeky4@mwandaSigned-off-by: Ingo Molnar <mingo@kernel.org>

kernel/events/core.c

@@ -9172,7 +9172,7 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 
 static struct pmu *perf_init_event(struct perf_event *event)
 {
-	struct pmu *pmu = NULL;
+	struct pmu *pmu;
 	int idx;
 	int ret;
 
@@ -9456,9 +9456,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	}
 
 	pmu = perf_init_event(event);
-	if (!pmu)
-		goto err_ns;
-	else if (IS_ERR(pmu)) {
+	if (IS_ERR(pmu)) {
 		err = PTR_ERR(pmu);
 		goto err_ns;
 	}