perf metricgroup: Use strsep()

No change in behaviour intended, trivial optimization done by avoiding
looking for spaces in 'g' right after setting it to "No_group".

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-f2siadtp3hb5o0l1w7bvd8bk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/metricgroup.c

@@ -308,10 +308,9 @@ void metricgroup__print(bool metrics, bool metricgroups, char *filter,
 				struct mep *me;
 				char *s;
 
+				g = skip_spaces(g);
 				if (*g == 0)
 					g = "No_group";
-				while (isspace(*g))
-					g++;
 				if (filter && !strstr(g, filter))
 					continue;
 				if (raw)