MIPS: ingenic: JZ4725B: Add IPU node

Add a devicetree node for the Image Processing Unit (IPU) found in the
JZ4725B. Connect it with graph nodes to the LCD node. The LCD driver
will expect the IPU node to be accessed through graph port #8, as stated
in the bindings documentation.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>