ASoC: Intel: Remove vague commit about slave DMA config from firmware loader

Intel MID DMA driver is going to be removed, commit should be a few lines
down near to dmaengine_slave_config() call in order to not confuse and at
quick look Synopsys DesignWare does seem to use some of the slave config
structure fields (see drivers/dma/dw/core.c: dwc_config()).

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>