gpu: ipu-v3: add DT binding for the Prefetch Resolve Engine

The Prefetch Resolve Engine is a prefetch and tile resolve engine
which prefetches display data from DRAM to an internal SRAM region.
It has a single clock for configuration register access and the
functional units. A single shared interrupt is used for status and
error signaling.

The only external dependency is the SRAM region to use for the
prefetch double buffer.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>