u-boot: Remapping linux early console logs

changed u-boot bootargs to remap linux early console logs from soc uart2 (s1 termial) to css non-secure (uart_ap terminal)

Change-Id: Ib78e1cdcabb24ff2a562cbfbcf834b8260bbf26d
Signed-off-by: Annam Sai Manisha <annam.saimanisha@arm.com>