rmnet_shs: Ignore Frag nonlinear packets

Rmnet_shs will try to incorrectly steer frag nonlinear skbs
this might cause reassembly errors and incorrects stats.

This change will cause rmnet_shs to correctly ignore nonlinear
skbs that are UDP/TCP frag packets.

CRs-Fixed: 2471725
Change-Id: Ifb325819ae91ff732ac7203d2dad8920b933206e
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>