net/iavf: replace SMP barrier with thread fence in Rx

net/iavf: replace SMP barrier with thread fence in Rx

Replace the SMP barrier with atomic thread fence for iavf hw ring scan
in the bulk Rx path.

This patch introduces a change to the iavf driver that was already added
to the i40e driver [1] as part of the adoption of the use of compiler
atomics.

[1]Commit 8649e2356689 ("net/i40e: replace SMP barrier with thread fence
in Rx")

Signed-off-by: Kathleen Capella <kathleen.capella@arm.com>
Reviewed-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Qi Zhang <qi.z.zhang@intel.com>