arm: zynq: Add an info message about post config

Post configuration cant be run at u-boot as u-boot
didn't has any info about the design.So,this patch
adds an info message that post config was not run
and needs to be run manually if needed.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>