perf debug: Remove needless include directives from debug.h

All we need there is a forward declaration for 'union perf_event', so
remove it from there and add missing header directives in places using
things from this indirect include.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-7ftk0ztstqub1tirjj8o8xbl@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/perf.c

@@ -10,6 +10,7 @@
 #include "builtin.h"
 #include "perf.h"
 
+#include "util/cache.h"
 #include "util/env.h"
 #include <subcmd/exec-cmd.h>
 #include "util/config.h"
@@ -32,6 +33,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <linux/kernel.h>
+#include <linux/string.h>
 #include <linux/zalloc.h>
 
 const char perf_usage_string[] =