Added LED toggling from the Rosalina misc. menu

sysmodules/rosalina/include/mcu.h

@@ -0,0 +1,9 @@
+#include <3ds.h>
+
+Handle mcuhwcHandle;
+
+Result mcuInit(void);
+Result mcuExit(void);
+Result mcuReadRegister(u8 reg, u8* data, u32 size);
+Result mcuWriteRegister(u8 reg, u8* data, u32 size);
+Result mcuGetLEDState(u8* out);