mtd: maps: rbtx4939-flash: fix compile error

We got the syntax wrong here. Compile tested this time!

Error:

drivers/mtd/maps/rbtx4939-flash.c: In function 'rbtx4939_flash_probe':
>> drivers/mtd/maps/rbtx4939-flash.c:99:11: error: request for member 'dev' in something not a structure or union
info->mtd.dev.parent = &dev->dev;
^

Fixes: 9aa7e50276c1 ("mtd: maps: rbtx4939-flash: show parent device in sysfs")
Reported-by: kbuild test robot <[e-mail]>
Signed-off-by: Brian Norris <[e-mail]>
Cc: Frans Klaver <[e-mail]>

drivers/mtd/maps/rbtx4939-flash.c

···
 		err = -ENXIO;
 		goto err_out;
 	}
-	info->mtd.dev.parent = &dev->dev;
+	info->mtd->dev.parent = &dev->dev;
 	err = mtd_device_parse_register(info->mtd, NULL, NULL, pdata->parts,
 					pdata->nr_parts);