net: rmnet_data: Skip UL aggregation for ping packets

ICMP packets could be potentially stuck behind aggregated traffic
if UL aggregation is enabled on rmnet_data. This results in
increased latencies during ping tests as the workqueues for these
packets are scheduled at non deterministic times.

CRs-Fixed: 2131879
Change-Id: I19208301b5674749aa2f1dee65a9226eda364c85
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>