nax: Avoid unnecessary calls to AsNCA() in IdentifyType()

AsNCA() allocates an NCA instance every time it's called. In the current
manner it's used, it's quite inefficient as it's making a redundant
allocation.

We can just amend the order of the conditionals to make it easier to
just call it once.

src/core/loader/nax.cpp

@@ -21,14 +21,18 @@ AppLoader_NAX::~AppLoader_NAX() = default;
 FileType AppLoader_NAX::IdentifyType(const FileSys::VirtualFile& file) {
     FileSys::NAX nax(file);
 
-    if (nax.GetStatus() == ResultStatus::Success && nax.AsNCA() != nullptr &&
-        nax.AsNCA()->GetStatus() == ResultStatus::Success) {
-        return FileType::NAX;
+    if (nax.GetStatus() != ResultStatus::Success) {
+        return FileType::Error;
     }
 
+    const auto nca = nax.AsNCA();
+    if (nca == nullptr || nca->GetStatus() != ResultStatus::Success) {
         return FileType::Error;
     }
 
+    return FileType::NAX;
+}
+
 ResultStatus AppLoader_NAX::Load(Kernel::SharedPtr<Kernel::Process>& process) {
     if (is_loaded) {
         return ResultStatus::ErrorAlreadyLoaded;