Docs/zh_CN: Translate physical_memory.rst to Simplified Chinese

This patch translates the "physical_memory.rst" document into
Simplified Chinese to improve accessibility for Chinese-speaking
developers and users.

Signed-off-by: Yaxin Wang <wang.yaxin@zte.com.cn>
Signed-off-by: Jiang Kun <jiang.kun2@zte.com.cn>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20241028135321916ZWK032bHhlbncjvmzDkZs@zte.com.cn