bluedroid_builcfg / ramdisk: take advantage of the new a2dp tuning

Using this now:
http://review.cyanogenmod.org/#/c/33594/
 #define A2DP_HW_SYSFS_TUNER "/sys/devices/platform/tegra_uart.2/a2dp_tuning"
 #define A2DP_HW_SYSFS_TUNER_OFF "0"
 #define A2DP_HW_SYSFS_TUNER_ON "1"

Change-Id: I5385847fdbd987074cc3dee4d0acfa18a6c4a244