Lower bluetooth output buffer size

The current bluetooth buffer is 10ms, resulting in a burst size of
441 frames. When this number is reduced to 2ms to be more inline
with the primary audio hal or the usb hal, the latency on a Boltune
headset on Bramble is lowered from 367ms to 337ms.

Bug: 196269772
Tag: #refactor
Test: Turn off bt offloading and test change manually
Change-Id: I5dbc6d7d1a69c5bc6ef8012095b4d964684761da