msm: IPA : Tethering offload clean up on MHI PRIME

This change does code clean up for tethering use cases such as
Rndis and WiFi on MHI Prime IPA offload path.

Change-Id: Iba9191ae8dcfdda79711327902d9df33550e7c69
Acked-by: Jyothij <jyothij@qti.qualcomm.com>
Signed-off-by: Michael Adisumarta <madisuma@codeaurora.org>