mtd: nand: jz4780: fixup, device structure assigned at probe

bch->dev is already assigned to &pdev->dev in the probe function.
Remove the duplicate assignment done in jz4780_bch_get().

Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@linaro.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Acked-by: Harvey Hunt <harvey.hunt@imgtec.com>