Rockbox

Since the audio engine refactoring, the crossfade process is often skipped for no obvious (to the user) reason. The existing code appears to be somewhat pessimistic about the amount of buffered data required to initiate a crossfade. There are various checks for .5s and 3s of data, and I believe the latter to be redundant (and probably the cause of the non-crossfades). This patch simply removes that test and is put here for further testing.