efi: Disable mirror feature during crashkernel

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8USBA


CVE: NA

--------------------------------

If system have no mirrored memory or use crashkernel.high while
kernelcore=mirror is enabled in cmdline, during crashkernel,
there will be limited mirrored memory and this usually lead to
OOM.

To solve this problem, disable mirror feature during crashkernel.

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>