wcd938x: add dummy widgets to codec inputs/output

With multicodec approach, codec widgets are added much earlier during sound
card registration than aux codec approach. The connections between bolero and wcd938x
are done via device tree at a later point. DAPM does power checkup for codec widgets
before the codec-codec path is connected. This results in wcd938x dapm inputs/output
to be considered as endpoints, which results in playback/record failure once after
bootup. Hence, add dummy output/input widgets to wcd938x dapm inputs/output which are not
codec endpoints.

Change-Id: I5ab4839e9b76adba24c9254ae56dc784b4448af7
Signed-off-by: Vignesh Kulothungan <vigneshk@codeaurora.org>