i9300: audio: force use both mics when back mic is selected

for video recording

Change-Id: Iaf8b878f7dc0a545ada41eab50962a945254c5f1
i9300: audio: increase mic gain

Change-Id: Ia54ed849ff54eae064717210065265e83a22595c
Merge branch 'cm-10.1' of git://github.com/CyanogenMod/android_device_samsung_i9300 into cm-10.1