ASoC: wcd9310: fix TRRS override

The debugfs TRRS entry is for overriding headset button polling.
Fix regression not to start button polling when this flag is set.

CRs-fixed: 386038
Change-Id: I469c366bc111f37ecbb46708d2800200dd3d7584
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>