ASoc: msm: MBHC skipped when using external headset detection

We don't need MBHC when using external headset detection. In that case,
skip the MBHC detection and then use external headset detection instead.

Change-Id: I1ad4a39f35d08ccbcb726e5171c7adc79c99ff73
Author: Hyunsub Na <hyunsub.na@lge.com>
Signed-off-by: Hyunsub Na <hyunsub.na@lge.com>
Signed-off-by: Devin Kim <dojip.kim@lge.com>