Coldfire targets: Shuffle IRQ levels around to have all interaction between low level...

Coldfire targets: Shuffle IRQ levels around to have all interaction between low level audio function calls and DMA be atomic. Make recording and playback independently startable and stoppable so one can be running and not interfere with the other. All tests I can do at the moment check out ok (play, record, play+record, FM radio on iRivers, S/PDIF on H120 (w/running optical on/off), and on-the-fly samplerate changes). Recording tested for well over an hour run and no problems.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@12658 a1c6a512-1295-4272-9138-f99709370657