samples: rust_dma: use vertical import style

Convert `use` imports to vertical layout for better readability and
maintainability.

Signed-off-by: Guru Das Srinagesh <linux@gurudas.dev>
Link: https://patch.msgid.link/20260721-rfl-vert-imp-v2-1-71ce0df519f2@gurudas.dev
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

samples/rust/rust_dma.rs

@@ -17,10 +17,14 @@
         io_read,
         Io, //
     },
-    page, pci,
+    page,
+    pci,
     prelude::*,
-    scatterlist::{Owned, SGTable},
-    sync::aref::ARef,
+    scatterlist::{
+        Owned,
+        SGTable, //
+    },
+    sync::aref::ARef, //
 };
 
 #[pin_data(PinnedDrop)]