perf ui gtk: Move gtk .so name to the only place where it is used

No need to pollute util.h with this.

Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-kec0chbdtgrd71o3oi2kz2zt@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/ui/setup.c

@@ -10,7 +10,10 @@ pthread_mutex_t ui__lock = PTHREAD_MUTEX_INITIALIZER;
 void *perf_gtk_handle;
 int use_browser = -1;
 
+#define PERF_GTK_DSO "libperf-gtk.so"
+
 #ifdef HAVE_GTK2_SUPPORT
+
 static int setup_gtk_browser(void)
 {
 	int (*perf_ui_init)(void);