ARM: dts: AM33XX: don't redefine OCP bus and device nodes

The On Chip Peripherals (OCP) device node is a simplified
representation of the AM33XX SoC interconnect. An OCP dev
node is already defined in the am33xx.dtsi Device Tree
source file included by am33xx based boards so there is
no need to redefine this on each board DT file.

Also, the OCP and IP modules directly connected to it are SoC
internal details that is better to keep outside of board files.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Benoit Cousson <bcousson@baylibre.com>