dmaengine: fsl-edma: fix for missing dmamux module

Fix following panic on system halt:

Requesting system halt
[   10.600000] spi spi0.1: spi_device 0.1 cleanup
[   10.630000] fsl_edma_chan_mux() fsl_chan->edma->n_chans 64 dmamux_nr 0
[   10.630000] *** ZERO DIVIDE ***   FORMAT=4
[   10.630000] Current process id is 38
[   10.630000] BAD KERNEL TRAP: 00000000
[   10.630000] PC: [<402f09ba>] fsl_edma_chan_mux+0x7c/0x12e
...

Some architecture as mcf5441x (ColdFire) may not have
a dmamux, so dmamux_nr is set to 0. This patch considers this case.
Signed-off-by: Angelo Dureghello <angelo.dureghello@timesys.com>
Link: https://lore.kernel.org/r/20210901211610.662077-1-angelo.dureghello@timesys.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/fsl-edma-common.c

@@ -638,11 +638,13 @@ EXPORT_SYMBOL_GPL(fsl_edma_alloc_chan_resources);
 void fsl_edma_free_chan_resources(struct dma_chan *chan)
 {
 	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
+	struct fsl_edma_engine *edma = fsl_chan->edma;
 	unsigned long flags;
 	LIST_HEAD(head);
 
 	spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
 	fsl_edma_disable_request(fsl_chan);
+	if (edma->drvdata->dmamuxs)
 		fsl_edma_chan_mux(fsl_chan, 0, false);
 	fsl_chan->edesc = NULL;
 	vchan_get_all_descriptors(&fsl_chan->vchan, &head);