msm: rndis_ipa: Remove rndis_ipa loopback functionality

Rndis_ipa loopback functionality at rndis_ipa driver
is a debug functionality that is not used.

Change-Id: Ibbcb26d3871cffeb46b028efcf4d428e88eb9e10
CRs-fixed: 1104431
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>