dma_channel_cleanup() function

Performs DMA channel cleanup after use This can be used to cleanup dma channels when they're no longer needed, such that they are in a clean state for reuse. IRQ's for the channel are disabled, any in flight-transfer is aborted and any outstanding interrupts are cleared. The channel is then clear to be reused for other purposes. \code if (dma_channel >= 0) { dma_channel_cleanup(dma_channel); dma_channel_unclaim(dma_channel); dma_channel = -1; } \endcode