audio: ble: volume computation improvement on BLE for notifications

BLE should behave the same as A2DP in this scenario.
When playing STRATEGY_SONIFICATION* streams, or system sounds or
  enforced sounds on A2DP/BLE during media playback, ensure the
  difference between the media volume and the notification
  is no more than 12dB.

Change-Id: Ib125e0266203212ced3aef0f8c4669e61dc4c6d7
Signed-off-by: chenxin20 <chenxin20@xiaomi.com>