The DPDK port will not have a link after the devbind which is needed for configuring an interface to be a DPDK port. The MTU is being committed during the link change but for DPDK ports there is no link.
The DPDK port MTU should be set on ovsdb right after the interface is added to ovsdb. This way the users will be able to set MTU for DPDK ports and modify it.
Please see the following results:
port 2: iface0 (dpdk: configured_rx_queues=1, configured_rxq_descriptors=2048, configured_tx_queues=3, configured_txq_descriptors=2048, lsc_interrupt_mode=false, mtu=2000, requested_rx_queues=1, requested_rxq_descriptors=2048, requested_tx_queues=3, requested_txq_descriptors=2048, rx_csum_offload=true, tx_tso_offload=false)