net/mlx5: fix Netlink communication routine

net/mlx5: fix Netlink communication routine

While receiving the Netlink reply messages we should stop at DONE
or ACK message. The existing implementation stops at DONE message
or if no multiple message flag set ( NLM_F_MULTI). It prevents
the single query requests from working, these requests send the
single reply message without multi-message flag followed by
ACK message. This patch fixes receiving part of Netlink
communication routine.

Fixes: 6e74990b3463 ("net/mlx5: update E-Switch VXLAN netlink routines")
Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
Acked-by: Shahaf Shuler <shahafs@mellanox.com>