net/ixgbe: fix link state timing on fiber ports

net/ixgbe: fix link state timing on fiber ports

In ixgbe_dev_link_update_share(), if the media type is fiber and the
link is down, a flag (IXGBE_FLAG_NEED_LINK_CONFIG) is set. A callback
to ixgbe_dev_setup_link_thread_handler() is scheduled which should
try to set up the link and clear the flag afterwards. This flag works
as a guard variable between threads.

To avoid potential race condition between threads, set the
IXGBE_FLAG_NEED_LINK_CONFIG flag only when there is no link thread
running.

Bugzilla ID: 388
Fixes: 819d0d1d57f1 ("net/ixgbe: fix blocking system events")
Cc: stable@dpdk.org
Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Lijian Zhang <lijian.zhang@arm.com>
Acked-by: Xiaolong Ye <xiaolong.ye@intel.com>