mtd: rawnand: davinci: stop using pdev->id as chipselect

All platform now use the core_chipsel field in platform data. Stop
using pdev->id in the driver.

Acked-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>