nand: increase chip_delay in mv kirkwood nand driver

The new SAMSUNG NAND Flash K9F1G08U0D require a bigger chip_delay.
The Data Transfer from Cell to Register is >= 35us. Other Vendors
and older chips normally use >= 25us. To have enough margin 40us
is selected.

Signed-off-by: Stefan Bigler <stefan.bigler@keymile.com>
Signed-off-by: Holger Brunck <holger.brunck@keymile.com>
cc: Prafulla Wadaskar <prafulla@marvell.com>
cc: Stefan Roese <sr@denx.de>
Signed-off-by: Scott Wood <scottwood@freescale.com>