qcacld-3.0: Packet stat collection failure

Change made I7fd67b02c3b7cb4f1bfe7c6f4641f6d881e25abd
to fix possible NULL dereference of pkt_stats_dump
caused pkt stats collection to fail as pkt_stats_dump
is NULL from cds_pkt_stats_to_logger_thread.

Move NULL check for pkt_stats_dump to just before
it is dereferenced

Change-Id: I0f4c9d58f0d4d17d6c26bfbbd79f6447dd52230b
CRs-Fixed: 2358139