misc: Fix clippy - manual implementation of ok

Reported by 1.86.0-beta.1 (f0cb41030 2025-02-17).

Signed-off-by: Ruoqing He <heruoqing@iscas.ac.cn>

arch/src/aarch64/fdt.rs

@@ -1109,10 +1109,7 @@ fn print_node(node: fdt_parser::node::FdtNode<'_, '_>, n_spaces: usize) {
         //   - At first, try to convert it to CStr and print,
         //   - If failed, print it as u32 array.
         let value_result = match CStr::from_bytes_with_nul(value) {
-            Ok(value_cstr) => match value_cstr.to_str() {
-                Ok(value_str) => Some(value_str),
-                Err(_e) => None,
-            },
+            Ok(value_cstr) => value_cstr.to_str().ok(),
             Err(_e) => None,
         };