s7: support onboot sign [1/1]

PD#SWPL-171076

Problem:
Samsung need split ddr out of bl2

Solution:
add on boot sign support

Verify:
local

Change-Id: I787d177613aa52a29bc410f41d5d0b043e82078a
Signed-off-by: Tao Zeng <tao.zeng@amlogic.com>
1 file changed