dmaengine: dw-edma: Drop unused dchan2dev() and chan2dev()

dmaengine: dw-edma: Drop unused dchan2dev() and chan2dev()

Static functions dchan2dev() and chan2dev() are not used, W=1 build:

  dw-edma-core.c:27:16: error: unused function 'dchan2dev' [-Werror,-Wunused-function]
  dw-edma-core.c:33:16: error: unused function 'chan2dev' [-Werror,-Wunused-function]

Fixes: e63d79d1ffcd ("dmaengine: Add Synopsys eDMA IP core driver")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20250525-dma-fixes-v1-1-89d06dac9bcb@linaro.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>