Port fix from dpdk official github (https://github.com/DPDK/dpdk/commit/a2efa4f66094c1fa78ac956bb065925ca263082a)
net/e1000: always enable receive and transmit

The transmit and receive controller state machines are only enabled after

receiving an interrupt and the link status is now valid.  If an adapter

is being used in conjunction with NC-SI, network controller sideband

interface, the adapter may never get a link state change interrupt since

the adapter's PHY is always link up and never changes state.
To fix this, always enable and disable the transmit and receive with

.dev_start and .dev_stop.  This is a better match for what is typically

done with the other PMD's.  Since we may never get an interrupt to check

the link state, we also poll once at the end of .dev_start to get the

current link status.