arm: dts: ls1021a: Share all MSIs

In order to maximize the use of MSI, a PCIe controller will share
all MSI controllers. The patch changes msi-parent to refer to all
MSI controller dts nodes.

Signed-off-by: Minghuan Lian <Minghuan.Lian@nxp.com>
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>