plat/arm/arm_image_load: fix bug of overriding the last node

The traverse flow in function plat_add_sp_images_load_info() will find
the last node in the main load info list, with its
next_load_info==NULL. However this node is still useful and should not
be overridden with SP node info.

The bug will cause below error on RDN2 for spmd enabled:

ERROR:   Invalid NT_FW_CONFIG DTB passed

Fix the bug by only setting the next_load_info of the last node in the
original main node list.

Signed-off-by: Heyi Guo <guoheyi@linux.alibaba.com>
Change-Id: Icaee5da1f2d53b29fdd6085a8cc507446186fd57
1 file changed