plugins HAVE_BACKLIGHT helper remove ifdefs in favor of dummy functions

lessen the ifdef hell

Change-Id: I52f830284e4599f3fc3a75c27dda27058b8de1a3

apps/plugins/xworld/sys.c

@@ -122,9 +122,8 @@ void exit_handler(void)
 #ifdef HAVE_ADJUSTABLE_CPU_FREQ
     rb->cpu_boost(false);
 #endif
-#ifdef HAVE_BACKLIGHT
+
     backlight_use_settings();
-#endif
 }
 
 static bool sys_do_help(void)
@@ -428,9 +427,8 @@ void sys_menu(struct System* sys)
 void sys_init(struct System* sys, const char* title)
 {
     (void) title;
-#ifdef HAVE_BACKLIGHT
+
     backlight_ignore_timeout();
-#endif
     rb_atexit(exit_handler);
     save_sys = sys;
     rb->memset(&sys->input, 0, sizeof(sys->input));