net/mlx4: fix no Rx interrupts

net/mlx4: fix no Rx interrupts

This commit addresses the issue of Rx interrupts support with
the new Rx datapath introduced in DPDK version 17.11.
In order to generate an Rx interrupt an event queue is armed with the
consumer index of the Rx completion queue. Since version 17.11 this
index is handled by the PMD so it is now the responsibility of the
PMD to write this value when enabling Rx interrupts.

Fixes: 6681b845034c ("net/mlx4: add Rx bypassing Verbs")

Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>