spi: dw-mid: remove redundant dmac member

Instead of using that member we prefer to use dma_dev which represents actual
struct device of the DMA device.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --cc drivers/spi/spi-dw-mid.c
Simple merge

diff --cc drivers/spi/spi-dw.h
Simple merge