net: ethernet: ti: cpsw: restore shaper configuration while down/up

Need to restore shapers configuration after interface was down/up.
This is needed as appropriate configuration is still replicated in
kernel settings. This only shapers context restore, so vlan
configuration should be restored by user if needed, especially for
devices with one port where vlan frames are sent via ALE.

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>