perf stat: Fix error check return value of hashmap__new(), must use IS_ERR()

hashmap__new() returns ERR_PTR(-ENOMEM) when it fails, so we should use
IS_ERR() to check it in error handling path.
Reported-by: NZeal Robot <zealci@zte.com.cn>
Signed-off-by: NLv Ruyi <lv.ruyi@zte.com.cn>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220413093302.2538128-1-lv.ruyi@zte.com.cnSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/stat.c

 // SPDX-License-Identifier: GPL-2.0
 #include <errno.h>
+#include <linux/err.h>
 #include <inttypes.h>
 #include <math.h>
 #include <string.h>
@@ -311,7 +312,7 @@ static int check_per_pkg(struct evsel *counter, struct perf_counts_values *vals,
 
 	if (!mask) {
 		mask = hashmap__new(pkg_id_hash, pkg_id_equal, NULL);
-		if (!mask)
+		if (IS_ERR(mask))
 			return -ENOMEM;
 
 		counter->per_pkg_mask = mask;