arm: dts: imx7: Fix error in coresight TPIU graph connection

OF graph endpoint connections must be bidirectional and dtc warn if they
are not. i.MX7 based DTs have an error and generate
warnings:

arch/arm/dts/imx7d-sdb.dtb: Warning (graph_endpoint):
/replicator/ports/port@0/endpoint: graph connection to node
'/soc/tpiu@30087000/port/endpoint' is not bidirectional
arch/arm/dts/imx7d-sdb.dtb: Warning (graph_endpoint):
/soc/tpiu@30087000/port/endpoint: graph connection to node
'/replicator/ports/port@1/endpoint' is not bidirectional

Signed-off-by: Ilko Iliev <iliev@ronetix.at>