[dts] [PATCH V1]tests/link_flowctrl: add the verification of Niantic card

[Tu, Lijuan]

> Subject: [dts] [PATCH V1]tests/link_flowctrl: add the verification of Niantic card
> 
> add the verification of Niantic card.
> fix incorrect verification that only enabling rx link flow control.
> 
> Signed-off-by: hanyingya <yingyax.han at intel.com>

Applied