net: Warn for cloned packets in ingress path on SMP systems only

GRO is currently enabled only on SMP systems so move the check for
cloned packets from commit b8a7d12f ("net: Warn for cloned
packets in ingress path") within CONFIG_RPS to prevent printing an
unnecessary warning on single core systems.

CRs-Fixed: 1006937
Change-Id: Ib8cb979136def6696861a7835bcde763dabe874f
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>