fs/ntfs3: Use variable length array instead of fixed size

Should fix smatch warning:
	ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)

Fixes: 4534a70b ("fs/ntfs3: Add headers and misc files")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202401091421.3RJ24Mn3-lkp@intel.com/Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/ntfs.h

@@ -59,7 +59,7 @@ struct GUID {
 struct cpu_str {
 	u8 len;
 	u8 unused;
-	u16 name[10];
+	u16 name[];
 };
 
 struct le_str {