let's call either nx_dup/nx_dup2 or file_dup/file_dup2 instead just like other fs api: xxx->nx_xxx->file_xxx Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com> Change-Id: I1aacfb9e25dc7b3fcb0345ff7b269b1953a01e5b