mtd: nand: ams-delta: Fix path to toto.c source file

Last known location of toto.c was drivers/mtd/nand/toto.c. Fix the
path so that one can use git log to find when the driver was deleted
and possibly checkout the source code.
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

drivers/mtd/nand/ams-delta.c

 /*
  *  Copyright (C) 2006 Jonathan McDowell <noodles@earth.li>
  *
- *  Derived from drivers/mtd/toto.c
+ *  Derived from drivers/mtd/nand/toto.c
  *  Converted to platform driver by Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
  *  Partially stolen from plat_nand.c
  *