kexec: Add quick kexec support for kernel

hulk inclusion
category: feature
bugzilla: 48159
CVE: N/A

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In normal kexec, relocating kernel may cost 5 ~ 10 seconds, to
copy all segments from vmalloced memory to kernel boot memory,
because of disabled mmu.

We introduce quick kexec to save time of copying memory as above,
just like kdump(kexec on crash), by using reserved memory
"Quick Kexec".

To enable it, we should reserve memory and setup quick_kexec_res.

Constructing quick kimage as the same as crash kernel,
then simply copy all segments of kimage to reserved memroy.

We also add this support in syscall kexec_load using flags
of KEXEC_QUICK.

Signed-off-by: Sang Yan <sangyan@huawei.com>
Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>