dmaengine: dmaengine_desc_callback_valid(): Check for `callback_result`

Before the `callback_result` callback was introduced drivers coded their
invocation to the callback in a similar way to:

if (cb->callback) {
spin_unlock(&dma->lock);
cb->callback(cb->callback_param);
spin_lock(&dma->lock);
}

With the introduction of `callback_result` two helpers where introduced to
transparently handle both types of callbacks. And drivers where updated to
look like this:

if (dmaengine_desc_callback_valid(cb)) {
spin_unlock(&dma->lock);
dmaengine_desc_callback_invoke(cb, ...);
spin_lock(&dma->lock);
}

dmaengine_desc_callback_invoke() correctly handles both `callback_result`
and `callback`. But we forgot to update the dmaengine_desc_callback_valid()
function to check for `callback_result`. As a result DMA descriptors that
use the `callback_result` rather than `callback` don't have their callback
invoked by drivers that follow the pattern above.

Fix this by checking for both `callback` and `callback_result` in
dmaengine_desc_callback_valid().

Fixes: f067025bc676 ("dmaengine: add support to provide error result from a DMA transation")
Signed-off-by: Lars-Peter Clausen <[e-mail]>
Acked-by: Dave Jiang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/dmaengine.h

···
 static inline bool
 dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
 {
-	return (cb->callback) ? true : false;
+	return cb->callback || cb->callback_result;
 }
 
 struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);