net/memif: move barrier outside loop
net/memif: move barrier outside loop

load-acquire memory order has a barrier. Loading it inside
the loop will result in a barrier in every iteration. Hence,
load the variable once outside the loop.

Signed-off-by: Honnappa Nagarahalli <01ccf438b971cc1d8919c8a7f18443cae9429d8b@arm.com>
Reviewed-by: Phil Yang <5a9b6465c065ff0e1fd5d2cb9eb2185e82f34247@arm.com>
Reviewed-by: Ruifeng Wang <a548d51fbc42485a8ba807711a537e88c2b59dd2@arm.com>
Reviewed-by: Jakub Grajciar <80f619e109c6efd382b3a6accd36cbd33d9669a2@cisco.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk