e1000: fix link power down

DPDK commit message

net/e1000/base: fix link power down
Current code is a result of work to reduce duplication between various
device models. However, the logic that was replaced did not exactly
match the new logic, and as a result the link power down was not
working correctly for some NICs, and the link remained up even when
the interface is down.

Fix it to correctly power down the link under all circumstances that
were supported by old logic.

Fixes: 44dddd1 ("net/e1000/base: remove duplicated codes")
Cc: stable@dpdk.org

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

Obtained from: DPDK (a8218d0)
MFC after: 1 week