Intel Haswell (and later) codec refreshes the widgets tree to expose
the whole widget nodes at probing.  However, this refresh was missing
for sysfs tree.

This patch adds the missing piece, as we have now a proper API.
Reported-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>