mtd: rawnand: mpc5121: Remove unused variable in ads5121_select_chip()

drivers/mtd/nand/raw/mpc5121_nfc.c: In function ‘ads5121_select_chip’:
drivers/mtd/nand/raw/mpc5121_nfc.c:294:19: warning: unused variable ‘mtd’ [-Wunused-variable]
  294 |  struct mtd_info *mtd = nand_to_mtd(nand);
      |                   ^~~

Fixes: 758b56f5

 ("mtd: rawnand: Pass a nand_chip object to chip->select_chip()")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20211122132138.3899138-1-geert@linux-m68k.org