btrfs: tree-checker: Fix error format string for size_t

Argument BTRFS_FILE_EXTENT_INLINE_DATA_START is defined as offsetof(),
which returns type size_t, so we need %zu instead of %lu.

This fixes a build warning on 32-bit ARM:

  ../fs/btrfs/tree-checker.c: In function 'check_extent_data_item':
  ../fs/btrfs/tree-checker.c:230:43: warning: format '%lu' expects argument of type 'long unsigned int', but argument 5 has type 'unsigned int' [-Wformat=]
    230 |     "invalid item size, have %u expect [%lu, %u)",
        |                                         ~~^
        |                                           long unsigned int
        |                                         %u

Fixes: 153a6d29 ("btrfs: tree-checker: Check item size before reading file extent type")
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andreas Färber <afaerber@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/tree-checker.c

@@ -227,7 +227,7 @@ static int check_extent_data_item(struct extent_buffer *leaf,
 	 */
 	if (item_size < BTRFS_FILE_EXTENT_INLINE_DATA_START) {
 		file_extent_err(leaf, slot,
-				"invalid item size, have %u expect [%lu, %u)",
+				"invalid item size, have %u expect [%zu, %u)",
 				item_size, BTRFS_FILE_EXTENT_INLINE_DATA_START,
 				SZ_4K);
 		return -EUCLEAN;