net/bonding: fix MTU set for slaves

net/bonding: fix MTU set for slaves

ethdev requires device to be configured before setting MTU.

In bonding PMD, while configuring slaves, bonding first sets MTU later
configures them, which causes failure if slaves are not configured in
advance.

Fixing by changing the order in slave configure as requested in ethdev
layer, configure first and set MTU later.

Bugzilla ID: 864
Fixes: b26bee10ee37 ("ethdev: forbid MTU set before device configure")
Cc: stable@dpdk.org
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Tested-by: Yu Jiang <yux.jiang@intel.com>
Acked-by: Min Hu (Connor) <humin29@huawei.com>