WIP "streaming" sampler

[enorrmann]

https://github.com/enorrmann/freetribe/tree/dv-sdcard-ipc/cpu/src/apps/sdcard

https://www.youtube.com/watch?v=tF5-QjHrys8

I'm working on a sampler that streams wav files directly from the sd card
on this example 16 first wave files from /samples/clean are asigned to the pads, but the data is only transfered via ipc when the pad is triggered
for now the file is fully buffered on an array so it's not really streaming but copying on the fly but for now its working
this uses the FAT code from @vananasun branch and also IPC from Maxim's branch
currently it pushes data from cpu to dsp ram via dev_dsp_ipc_transfer
I also tried writing cpu memory from dsp via dev_cpu_ipc_request_data but that didn't work, the function returns 0 OK but the callback is never called
perhaps because this is built on the new DEV branch in which cpu code runs from DDR ram but that's just a guess
cpu.bin.zip