perf ui browser map: Provide feedback on unhandled hotkeys

Don't just eat unknown keys without providing visual feedback and
instructions on how to see which ones are assigned.

Suggested-by: Ingo Molnar <[e-mail]>
Tested-by: Ingo Molnar <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Ian Rogers <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/browsers/map.c

···
 		case '/':
 			if (verbose > 0)
 				map_browser__search(browser);
+			/* fall thru */
 		default:
-			break;
+			ui_browser__warn_unhandled_hotkey(&browser->b, key, 0, NULL);
+			continue;
                 case K_LEFT:
                 case K_ESC:
                 case 'q':