perf hists browser: Inform how to reset the symbol filter

When in the hists browser, i.e. in 'perf report' or in 'perf top', it is
possible to press '/' and specify a substring to filter by symbol name.

Clarify how to remove a filter by making the prompt be:

   Please enter the name of symbol you want to see.
   To remove the filter later, press / + ENTER

Cc: Adrian Hunter <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/ui/browsers/hists.c

@@ -1889,7 +1889,8 @@ static int perf_evsel__hists_browse(struct perf_evsel *evsel, int nr_events,
 			continue;
 		case '/':
 			if (ui_browser__input_window("Symbol to show",
-					"Please enter the name of symbol you want to see",
+					"Please enter the name of symbol you want to see.\n"
+					"To remove the filter later, press / + ENTER.",
 					buf, "ENTER: OK, ESC: Cancel",
 					delay_secs * 2) == K_ENTER) {
 				hists->symbol_filter_str = *buf ? buf : NULL;