arm: ls1028a: define the integrated PCI bus (ECAM)

arm: ls1028a: define the integrated PCI bus (ECAM)

LS1028A includes an integrated PCI bus with 11 PCI functions residing on
bus 0.  ECAM plus the device register space takes up 256MB of address
space.

Signed-off-by: Alex Marginean <alexm.osslist@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>