net: Add memory barriers to prevent possible race in byte queue limits

net: Add memory barriers to prevent possible race in byte queue limits

[ Upstream commit b37c0fbe3f6dfba1f8ad2aed47fb40578a254635 ]

This change adds a memory barrier to the byte queue limit code to address a
possible race as has been seen in the past with the
netif_stop_queue/netif_wake_queue logic.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>