xlnx-zynqmp: Connect the four OCM banks

The Xilinx EP108 has four separate OCM banks which are located
adjacent to each other. This patch adds the four banks to
the ZynqMP SoC.

Signed-off-by: Alistair Francis <alistair.francis@xilinx.com>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: afa6ba31163a5d541a0bef4b0dc11f2597e0c495.1436813543.git.alistair.francis@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>