d2: Squashed revert of msm_serial_hs.c updates

Reverts d0351295f9774e837d9bd05469ba90a0bac77667 and 9fcb8efb0242207c91e8fe1179f806ae2fb6fb1b

Commit 9fcb8efb0242207c91e8fe1179f806ae2fb6fb1b is causing issues with Bluetooth issues on d2 devices (d2vzw primarily)

- Pairing issues with pair failures
- Handshaking issues after pairing with device timing out or numerious retry to connect
- Disconnect issues - lack of reconnecting issues

Revert confirms fix on d2vzw

Change-Id: I88df917560a7cfe03ff5da6e54c9af89bba6962b