mtd: nand: gpio: Fix ALE gpio configuration

Fixes a copy/paste error in commit f3d0d8d9 ("mtd: nand: gpio:
Convert to use GPIO descriptors") which breaks gpio-nand driver

Fixes: f3d0d8d9 ("mtd: nand: gpio: Convert to use GPIO descriptors")
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Richard Weinberger <richard@nod.at>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Richard Weinberger <richard@nod.at>