ALSA: hdac: structure definition for ext_dma_params

This extends the structure definition of ext_device and adds
definition for dma_params which will be used when hdmi codec.

Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>