Revert "net: qualcomm: rmnet: Skip processing loopback packets"

This reverts commit a0ab962b.

This is a preparation change for merging android-4.14-p.79 into
msm-4.14 branch.

Same change is already presented in msm-4.14 via:

  79ea4b32 net: qualcomm: rmnet: Skip processing loopback packets

Change-Id: I3117de836a649186e078be52dd75d89456a622eb
Signed-off-by: Blagovest Kolenichev <bkolenichev@codeaurora.org>