tools: Adopt __scanf from kernel sources

To have a more compact way to ask the compiler to perform scanf like
argument validation.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/include/linux/compiler-gcc.h

···
 #define __noreturn	__attribute__((noreturn))
 
 #define __printf(a, b)	__attribute__((format(printf, a, b)))
+#define __scanf(a, b)	__attribute__((format(scanf, a, b)))

tools/perf/util/pmu.h

···
 #define __PMU_H
 
 #include <linux/bitmap.h>
+#include <linux/compiler.h>
 #include <linux/perf_event.h>
 #include <stdbool.h>
 #include "evsel.h"
···
 		      bool long_desc, bool details_flag);
 bool pmu_have_event(const char *pname, const char *name);
 
-int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt,
-			...) __attribute__((format(scanf, 3, 4)));
+int perf_pmu__scan_file(struct perf_pmu *pmu, const char *name, const char *fmt, ...) __scanf(3, 4);
 
 int perf_pmu__test(void);