find: Fix -fstype with stacked mounts

If you stack two mounts on top of each other, e.g.

    # mount -t ext4 /dev/sdX /mnt
    # mount -t f2fs /dev/sdY /mnt

then read_fs_list() will return two entries for that mount point.  The
later one is the one with the correct type, since the later mount is on
top of the earlier one.

src/find/matchers/fs.rs

@@ -53,7 +53,8 @@ pub fn get_file_system_type(path: &Path, cache: &RefCell<Option<Cache>>) -> URes
     let fs_list = uucore::fsext::read_fs_list()?;
     let result = fs_list
         .into_iter()
-        .find(|fs| fs.dev_id == dev_id)
+        .filter(|fs| fs.dev_id == dev_id)
+        .next_back()
         .map_or_else(String::new, |fs| fs.fs_type);
 
     // cache the latest query if not a match before

src/find/matchers/printf.rs

@@ -451,7 +451,8 @@ fn format_directive<'entry>(
                 uucore::fsext::read_fs_list().expect("Could not find the filesystem info");
             fs_list
                 .into_iter()
-                .find(|fs| fs.dev_id == dev_id)
+                .filter(|fs| fs.dev_id == dev_id)
+                .next_back()
                 .map_or_else(String::new, |fs| fs.fs_type)
                 .into()
         }