lib/env_dpdk: add rte_net dependency

Vhost is enabled by default, so rte_net was always included.
When disabled, rte_power failed as it depends on rte_ethdev and rte_net.

rte_vhost was only possible to enable on Linux, so there
is no conflict with adding it next to rte_power under this condition.

Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Change-Id: I2e183004d6457e404471740a0540dcb08aa738d8
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/6398


Reviewed-by: Ziye Yang <ziye.yang@intel.com>
Reviewed-by: Jacek Kalwas <jacek.kalwas@intel.com>
Reviewed-by: Nick Connolly <nick.connolly@mayadata.io>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot