ASoC: msm: 8x10: Adjust button range for button 7

With very fast press of button 7, it is found that
the measured voltage falls few mv below the lower
threshold. Adjust the threshold to detect the button
press.

Change-Id: I2d23607df9b3b7e993da214961f25fbadcffd60c
CRs-Fixed: 611825
Signed-off-by: Simmi Pateriya <simmip@codeaurora.org>