perf ui browsers: Add missing include

This file needs the K_{RIGHT,etc} definitions but isn't including the
file where they are defined, ui/keysyms.h, fix it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-jlpybqegpdauzx64l9r1jgm3@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/ui/browsers/header.c

 #include "util/cache.h"
 #include "util/debug.h"
 #include "ui/browser.h"
+#include "ui/keysyms.h"
 #include "ui/ui.h"
 #include "ui/util.h"
 #include "ui/libslang.h"