ARM: dts: am335x: Disable wait pin monitoring for NAND

The NAND Ready/Busy# line is connected to GPMC_WAIT0 pin and
can't be used for wait state insertion for NAND I/O read/write.
So disable read/write wait monitoring as per Reference Manual's
suggestion [1].

[1] AM335x TRM: SPRUH73L: 7.1.3.3.12.2 NAND Device-Ready Pin

Cc: Teresa Remmet <t.remmet@phytec.de>
Cc: Ilya Ledvich <ilya@compulab.co.il>
Cc: Yegor Yefremov <yegorslists@googlemail.com>
Cc: Rostislav Lisovy <lisovy@gmail.com>
Cc: Enric Balletbo i Serra <eballetbo@iseebcn.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>