samples: rust: use module_fs macro in sample

This eliminates the need to implement the `kernel::Module` trait as one
is provided by the fs module through the macro.

Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>

Author: wedsonaf

samples/rust/rust_rofs.rs

@@ -3,10 +3,10 @@
 //! Rust read-only file system sample.
 
 use kernel::prelude::*;
-use kernel::{c_str, fs, macros::pin_data};
+use kernel::{c_str, fs};
 
-module! {
-    type: RoFsModule,
+kernel::module_fs! {
+    type: RoFs,
     name: "rust_rofs",
     author: "Rust for Linux Contributors",
     description: "Rust read-only file system sample",
@@ -17,17 +17,3 @@ struct RoFs;
 impl fs::FileSystem for RoFs {
     const NAME: &'static CStr = c_str!("rust-fs");
 }
-
-#[pin_data]
-struct RoFsModule {
-    #[pin]
-    fs_reg: fs::Registration,
-}
-
-impl kernel::InPlaceModule for RoFsModule {
-    fn init(module: &'static ThisModule) -> impl PinInit<Self, Error> {
-        try_pin_init!(Self {
-            fs_reg <- fs::Registration::new::<RoFs>(module),
-        })
-    }
-}