1，VFS代码中不修改参数增加const修饰
2，fs_file_mapping.c: 增加安全函数的判空
3，path_cache.c: sizeof改为使用类型
4，fs_syscall.c: 对NULL解引用
5，VnodeLookup：冗余的判空，及不正确的判空

close: I3UMWD
Signed-off-by: yansira <yansira@hotmail.com>

fix typos length、there、necessary

close https://gitee.com/openharmony/kernel_liteos_a/issues/I3RSY0

Bug: #I3NEVN
Test:

Change-Id: I052d930d54e63179b17b77f02c107a015f3cfc3f

Feature or Bugfix:Feature
Binary Source:Huawei
PrivateCode(Yes/No):Yes

Change-Id: I175d2648bc6f9078c34de2c0a5c93fda10b86c47
ChangeID:13306388