mtd: parsers: Fix potential memory leak in mtd_parser_tplink_safeloader_parse()

The parts needs to be freed with all its elements, otherwise it will be
leaked.

Fixes: 00a35880

 ("mtd: parsers: add TP-Link SafeLoader partitions table parser")
Signed-off-by: Yuan Can <yuancan@huawei.com>
Reviewed-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20221208113620.78855-1-yuancan@huawei.com