serrano: Disable low latency recording

Change-Id: I74d4cea1d5d522f5d5c219ef63c484963b7aa2f2
serrano: Update some init scripts

Change-Id: Iaf948e4eb05521db2fec2973ec8ba390622a0d37
serrano: Increase MMC read ahead to 256kb

Change-Id: I18d2f08a61ed09c82abc026dea857a6bebffd4b9