Documentation: Fixes a term's translation in Documentation/zh_CN/arm64/memory.txt

Fixes a term's translation in Documentation/zh_CN/arm64/memory.txt
The modification is based on Catalin Marinas <catalin.marinas@arm.com>'s
suggestion:
    "memory" in "ffffffc000000000 ffffffffffffffff 256GB memory"
    should  be treated as "kernel logical memory map",
    so the translation should be "内核逻辑内存映射".

Signed-off-by: Fu Wei <tekkamanninja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/zh_CN/arm64/memory.txt

@@ -61,7 +61,7 @@ ffffffbe00000000	ffffffbffbffffff	  ~8GB		[防护页，未来用于 vmmemap]
 
 ffffffbffc000000	ffffffbfffffffff	  64MB		模块
 
-ffffffc000000000	ffffffffffffffff	 256GB		内存空间
+ffffffc000000000	ffffffffffffffff	 256GB		内核逻辑内存映射
 
 
 4KB 页大小的转换表查找：