net/i40e: fix link status update

net/i40e: fix link status update

This patch fixes link status update problem in interrupt mode.
Previously, directly reading link status register instead of
accessing via admin queue command may cause the link status
change interrupt callback inactive. This patch fixes the
problem by making the driver only read the register in
"no wait" and polling mode.

Bugzilla ID: 54
Fixes: eef2daf2e199 ("net/i40e: fix link update no wait")
Cc: stable@dpdk.org
Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>
Tested-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>