docs/zh_CN: add core-api memory-allocation translation

Translate Documentation/core-api/memory-allocation.rst into Chinese.

Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Alex Shi <alexs@kernel.org>
Link: https://lore.kernel.org/r/e3d30d816be4404b1bd2c728ec70cd3c2d6e5def.1631846923.git.siyanteng@loongson.cn


Signed-off-by: Jonathan Corbet <corbet@lwn.net>