zynqmp: add support for multi console interface

This patch addds multi console interface for ZynqMP
platform

Change-Id: I508a61412df2b71d04bca6a1139c8f32cbd7dccd
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Tested-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>