For the existing IOdelay configuration via U-Boot, NAND is
not supported on dra72-evm (both Rev B and Rev C).

Disable it. Commit 46cfc894 ("ARM: dts: dra72-evm: Remove
pinmux configurations for erratum i869") has already removed
pinmuxing for NAND making it unusable.
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>