ARM: zynq: Correct the smc nor memory region size

Corrected the smc nor memory region size as per the zynq trm

Signed-off-by: Punnaiah Choudary Kalluri <punnaia@xilinx.com>
Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>