nso: Return an optional address from LoadModule

If a malformed NSO is attempted to be loaded, we shouldn't continue
onwards. We should be reporting an error and bailing out.

src/core/loader/loader.h

@@ -90,6 +90,7 @@ enum class ResultStatus : u16 {
     ErrorNoRomFS,
     ErrorIncorrectELFFileSize,
     ErrorLoadingNRO,
+    ErrorLoadingNSO,
     ErrorNoIcon,
     ErrorNoControl,
     ErrorBadNAXHeader,