dmaengine: stm32-mdma: memset stm32_mdma_chan_config struct before using it

New bool m2m_hw has been added at the end of stm32_mdma_chan_config struct
to support the STM32 DMA MDMA chaining.

m2m_hw is set true in stm32_mdma_slave_config() if peripheral_size is set,
but m2m_hw is never initialized false.

To ensure this case, and any further new update of the structure, memset it
to 0 before using it.

Fixes: 6968743227 ("dmaengine: stm32-mdma: add support to be triggered by STM32 DMA")
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20221017131413.202567-1-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-mdma.c

@@ -1539,6 +1539,7 @@ static struct dma_chan *stm32_mdma_of_xlate(struct of_phandle_args *dma_spec,
 		return NULL;
 	}
 
+	memset(&config, 0, sizeof(config));
 	config.request = dma_spec->args[0];
 	config.priority_level = dma_spec->args[1];
 	config.transfer_config = dma_spec->args[2];