dmaengine: of: constify of_phandle_args in of_dma_find_controller()

of_dma_find_controller() does not modify passed of_phandle_args so the
argument can be made pointer to const for code safety.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240208202742.631307-2-krzysztof.kozlowski@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/of-dma.c

@@ -29,7 +29,7 @@ static DEFINE_MUTEX(of_dma_lock);
  * to the DMA data stored is retuned. A NULL pointer is returned if no match is
  * found.
  */
-static struct of_dma *of_dma_find_controller(struct of_phandle_args *dma_spec)
+static struct of_dma *of_dma_find_controller(const struct of_phandle_args *dma_spec)
 {
 	struct of_dma *ofdma;