net/iavf: fix race condition with Rx timestamp offload

net/iavf: fix race condition with Rx timestamp offload

In multi-cores cases for Rx timestamp offload, if packets arrive
too fast, aq command to get phc time will be pended.

This patch adds spinlock to fix this issue. To avoid phc time being
frequently overwritten, move related variables to iavf_rx_queue
structure, and each queue will handle timestamp calculation by itself.

Fixes: b5cd735132f6 ("net/iavf: enable Rx timestamp on flex descriptor")
Fixes: 33db16136e55 ("net/iavf: improve performance of Rx timestamp offload")
Signed-off-by: Wenjun Wu <wenjun1.wu@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>