Don't run EmulatedBS2_Wii with VolumeDirectory

VolumeDirectory doesn't support necessities like TMDs,
so thanks to 5.0-2172 (18968ab), EmulatedBS2_Wii crashes
when the inserted disc is a VolumeDirectory.
This commit fixes that.

This commit makes our DOL booting code very similar to our
ELF booting code. One exception is that the DOL booting
code still always calls SetupBAT. (Note that EmulatedBS2_GC
calls SetupBAT even if no disc is inserted.) I'm not sure
if there's a point to the difference, but I thought I'd
better avoid changing it so that I don't break anything.

Source/Core/Core/Boot/Boot.cpp

@@ -354,18 +354,24 @@ bool CBoot::BootUp()
       volume = SetDisc(DiscIO::CreateVolumeFromFilename(_StartupPara.m_strDefaultISO));
     }
 
-    if (!EmulatedBS2(dolWii, volume))
+    // Poor man's bootup
+    if (dolWii)
     {
-      if (dolWii)
-        HID4.SBE = 1;
+      HID4.SBE = 1;
       SetupBAT(dolWii);
 
-      if (dolWii)
-        SetupWiiMemory(volume, 0x000000010000003a);
-
-      dolLoader.Load();
-      PC = dolLoader.GetEntryPoint();
+      // Because there is no TMD to get the requested system (IOS) version from,
+      // we default to IOS58, which is the version used by the Homebrew Channel.
+      SetupWiiMemory(volume, 0x000000010000003a);
     }
+    else
+    {
+      EmulatedBS2_GC(volume, true);
+    }
+
+    Load_FST(dolWii, volume);
+    dolLoader.Load();
+    PC = dolLoader.GetEntryPoint();
 
     if (LoadMapFromFilename())
       HLE::PatchFunctions();