dma: nxp: sdma: Initialize channel capacity with zero

DMA channel capacity wasn't properly initialized and the computation
relies on it being zeroed.

This only works fine only when requesting channel the first time
causing problems when we have multiple cycles of channel
request/release.

Fix this by properly initializing the capacity when requesting the
channel.

Fixes 43a48d4 ("drivers: dma: sdma: Update buffer descriptor")
Signed-off-by: Daniel Baluta <[email protected]>

Author: dbaluta

drivers/dma/dma_nxp_sdma.c

@@ -432,6 +432,7 @@ static bool sdma_channel_filter(const struct device *dev, int chan_id, void *par
 
 	dev_data->chan[chan_id].event_source = *((int *)param);
 	dev_data->chan[chan_id].index = chan_id;
+	dev_data->chan[chan_id].capacity = 0;
 
 	return true;
 }