ETRAX-FS: Add support for DMA channel resets, needed for recent linux kernels.

* Correct numeric value for the RST state.
* Add emulation for reseting a DMA channel.
* Add a few sanity checks.
* Make it compile with debug enabled.



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5147 c046a42c-6fe2-441c-8c8c-71466251a162
