NetPlay: Split save and SD card write settings

This actually eliminates any setting pertaining to SD cards from the
NetPlay dialog, as it would effectively just be a duplicate of the
setting in the Wii pane, potentially causing confusion.

This also enables save data writing by default, as this is probably
what most players want, and should avoid them losing hours of progress
because they forgot to tick a checkbox.

Source/Core/Core/ConfigManager.h

@@ -119,7 +119,6 @@ struct SConfig
   bool bSyncGPUOnSkipIdleHack = true;
   bool bHLE_BS2 = true;
   bool bEnableCheats = false;
-  bool bEnableMemcardSdWriting = true;
   bool bCopyWiiSaveNetplay = true;
 
   bool bDPL2Decoder = false;