ASoC: wcd-mbhc: change special headset detection count

During slow insertion of headphone, it is detected as
special headset. So increase special headset count
so that headphone is detected correctly

CRs-Fixed: 1052600
Change-Id: I4d8230b2789e0a89d11c8a789511b5a99cd19e67
Signed-off-by: Yeleswarapu Nagaradhesh <nagaradh@codeaurora.org>