Replace .map() + .flatten() with .and_then()

src/platform/linux_usbfs/enumeration.rs

@@ -175,10 +175,7 @@ pub fn list_buses() -> Result<impl Iterator<Item = BusInfo>, Error> {
             path: rh.path.to_owned(),
             parent_path: parent_path.to_owned(),
             busnum: rh.busnum,
-            controller_type: driver
-                .as_ref()
-                .map(|p| UsbControllerType::from_str(p))
-                .flatten(),
+            controller_type: driver.as_ref().and_then(|p| UsbControllerType::from_str(p)),
             driver,
             root_hub: rh,
         })

src/platform/windows_winusb/enumeration.rs

@@ -404,8 +404,7 @@ fn parse_root_hub_id(s: &OsStr) -> Option<(u16, Option<String>)> {
         .unwrap_or((0x0110, 0)); // default USB 1.1
     let id = s
         .get(i..)
-        .map(|v| v.strip_prefix("\\").map(|s| s.to_owned()))
-        .flatten();
+        .and_then(|v| v.strip_prefix("\\").map(|s| s.to_owned()));
     Some((version, id))
 }