devlink: Fix per port reporter fields initialization

Cited patch in fixes tag initializes reporters_list and reporters_lock
of a devlink port after devlink port is added to the list. Once port
is added to the list, devlink_nl_cmd_health_reporter_get_dumpit()
can access the uninitialized mutex and reporters list head.
Fix it by initializing port reporters field before adding port to the
list.

Fixes: f4f54166 ("devlink: Implement devlink health reporters on per-port basis")
Signed-off-by: Parav Pandit <parav@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>