net/mlx4: add link up/down callback functions
net/mlx4: add link up/down callback functions

Implement dev_set_link_up and dev_set_link_down device
operations. Code is inspired by mlx5 implementations.

Signed-off-by: Fengtian Guo <3bae3a86339a84f93a6f4d56fc6008056a3ea53b@6wind.com>
Acked-by: Adrien Mazarguil <9d39ea493ca46c560334f650ac5d4b5ffbcb5cf0@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk