Align node properties to kernel dts node.

Keep U-Boot specific nand-enable-arbiter, and num-cs for compatibility
with the current driver.
Reviewed-by: NStefan Roese <sr@denx.de>
Signed-off-by: NShmuel Hazan <shmuel.h@siklu.com>
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>