policy_hal: remove VGS check for BT volume

-Currently voice volume is forced to MAX when VGS is set for BT.
 But VGS parameter is not used anymore in BT stack so it never
 set the value.
-Removed VGS check as this is deprecated and keep the behavior
 same as default policy.

Change-Id: I69de60987835cc7bfbf26e6b89eb39447423fd9d