arm64: Add support for memmap kernel parameters

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8NIMB



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Add support for memmap kernel parameters for ARM64. The three below
modes are supported:

memmap=exactmap
Enable setting of an exact memory map, as specified by the user.

memmap=nn[KMG]@ss[KMG]
Force usage of a specific region of memory.

memmap=nn[KMG]$ss[KMG]
Region of memory to be reserved is from ss to ss+nn, the region must
be in the range of existed memory, otherwise will be ignored.

If users set memmap=exactmap before memmap=nn[KMG]@ss[KMG], they will
get the exact memory specified by memmap=nn[KMG]@ss[KMG]. For example,
on one machine with 4GB memory, "memmap=exactmap memmap=1G@1G" will
make kernel use the memory from 1GB to 2GB only.

Please note that the above functions are for debugging purposes only.

Signed-off-by: Ze Zuo <zuoze1@huawei.com>