spi: dw-mid: switch to new dmaengine_terminate_* API (part 2)

The commit a3ff9582 ("spi: dw-mid: switch to new dmaengine_terminate_*
API") converted mid_spi_dma_exit() but missed mid_spi_dma_stop().

This is follow up to convert the rest.

Fixes: a3ff9582 ("spi: dw-mid: switch to new dmaengine_terminate_* API")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>