efi: Disable mirror feature if kernelcore is not specified

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4PM01


CVE: NA

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With this patch, kernel will check mirrored_kernelcore before calling
efi_find_mirror() which will enable basic mirrored feature.

If system have some mirrored memory and mirrored feature is not specified
in boot parameter, the basic mirrored feature will be enabled and this will
lead to the following situations:

- memblock memory allocation perfers mirrored region. This may have some
  unexpected influence on numa affinity.

- contiguous memory will be splited into server parts if parts of them
is mirrored memroy via memblock_mark_mirror().

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>