[ARM] 5400/1: Add support for inverted rdy_busy pin for Atmel nand device controller

Add support for inverted rdy_busy pin for Atmel nand device controller
It will fix building error on NeoCore926 board.

Acked-by: Andrew Victor <linux@maxim.org.za>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Gregory CLEMENT <gclement@adeneo.adetelgroup.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>