selftests: memfd: Align STACK_SIZE for ARM AArch64 system

The stack size should be 16 bytes aligned in arm64 system. The similar
patch has been merged already.

> <commit id: 1f78dda2cf5e4eeb00aee2a01c9515e2e704b4c0>
> selftests: memfd_test: Revised STACK_SIZE to make it 16-byte aligned
>
> There is a mandate of 16-byte aligned stack on AArch64 [1], so the
> STACK_SIZE here should also be 16-byte aligned, otherwise we would
> get an error when calling clone().
>
> [1] http://lxr.free-electrons.com/source/arch/arm64/kernel/process.c#L265
>
> Signed-off-by: Chunyan Zhang <[e-mail]>
> Acked-by: Arnd Bergmann <[e-mail]>
> Signed-off-by: Shuah Khan <[e-mail]>

Signed-off-by: Orson Zhai <[e-mail]>
Reviewed-by: Sumit Semwal <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/memfd/fuse_test.c

···
 #include <unistd.h>
 
 #define MFD_DEF_SIZE 8192
-#define STACK_SIZE 65535
+#define STACK_SIZE 65536
 
 static int sys_memfd_create(const char *name,
 			    unsigned int flags)