CHG: [droid] Splash.java: check sdcard readyness + refactor

I tried to do something similar in the native startup code (with JNI) when I worked on the android port and failed as well. It just looks like very bad design that the internal flash is detected as an external device because it's basically a flash device like an (micro)SD card.

Well I don't maintain this code so I'm not the one to decide. I usually just think that dead code makes it more difficult and confusing to maintain code.