mtd: rawnand: diskonchip: fix a potential double free in doc_probe

mtd: rawnand: diskonchip: fix a potential double free in doc_probe

When nand_scan() fails, it has cleaned up related resources
in its error paths. Therefore, the following nand_cleanup()
may lead to a double-free. One possible trace is:

doc_probe
  |-> nand_scan
  |     |-> nand_scan_with_ids
  |           |-> nand_scan_tail
  |                 |-> kfree(chip->data_buf) [First free]
  |
  |-> nand_cleanup
        |-> kfree(chip->data_buf) [Double free here]

Fix this by removing nand_cleanup() on failure of
nand_scan().

Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20231214072946.10285-1-dinghao.liu@zju.edu.cn