In preparation for register a PCM device for each pipe adjust
link up the ctl elements with the corresponding PCM device.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-10-ville.syrjala@linux.intel.comReviewed-by: NTakashi Iwai <tiwai@suse.de>