[Linux-stable-mirror] dmaengine: dmatest: warn user when dma test times out

a9df21e34b42 ("dmaengine: dmatest: warn user when dma test times out")

for 4.14-stable (applies cleanly) for 4.13-stable (applies cleanly)

This should be included since it warns the user that the kernel stack memory may have been corrupted due to a fault DMA callback.

I could also backport for older 4.x kernels if you think it would be useful.