btrfs: sysfs: fix format string for some discard stats

The type of discard_bitmap_bytes and discard_extent_bytes is u64 so the
format should be %llu, though the actual values would hardly ever
overflow to negative values.
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/sysfs.c

@@ -429,7 +429,7 @@ static ssize_t btrfs_discard_bitmap_bytes_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%lld\n",
+	return scnprintf(buf, PAGE_SIZE, "%llu\n",
 			fs_info->discard_ctl.discard_bitmap_bytes);
 }
 BTRFS_ATTR(discard, discard_bitmap_bytes, btrfs_discard_bitmap_bytes_show);
@@ -451,7 +451,7 @@ static ssize_t btrfs_discard_extent_bytes_show(struct kobject *kobj,
 {
 	struct btrfs_fs_info *fs_info = discard_to_fs_info(kobj);
 
-	return scnprintf(buf, PAGE_SIZE, "%lld\n",
+	return scnprintf(buf, PAGE_SIZE, "%llu\n",
 			fs_info->discard_ctl.discard_extent_bytes);
 }
 BTRFS_ATTR(discard, discard_extent_bytes, btrfs_discard_extent_bytes_show);