fs.mitm: Implement basic passthrough framework for input commands.

stratosphere/loader/source/ldr_main.cpp

@@ -75,6 +75,8 @@ void __appInit(void) {
         fatalSimple(0xCAFE << 4 | 0xFF);
         /* TODO: Does Loader need to know about target firmware/master key revision? If so, extract from exosphere_cfg. */
     }
+    
+    splExit();
 }
 
 void __appExit(void) {