arm32: kaslr: Adapt dts files of multiple memory nodes

hulk inclusion
category: bugfix
bugzilla: 47952
CVE: NA

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The dts files of some boards may have mutiple memory nodes,
so when calculating the offset value of kaslr, we need to
consider the memory layout, and choose the memory node where
the zImage is located.

Signed-off-by: Cui GaoSheng <cuigaosheng1@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>