powerpc/fsl_booke/kaslr: Fix preserved memory size for int-vectors issue

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8OHAZ



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The first 32k of memory is reserved for interrupt vectors, however for
powerpc64 this is not enough. Fix this by reserving the real size of
interrupt vectors.

Signed-off-by: GUO Zihua <guozihua@huawei.com>