accel: Add Arm Ethos-U NPU driver

Add a driver for Arm Ethos-U65/U85 NPUs. The Ethos-U NPU has a
relatively simple interface with single command stream to describe
buffers, operation settings, and network operations. It supports up to 8
memory regions (though no h/w bounds on a region). The Ethos NPUs
are designed to use an SRAM for scratch memory. Region 2 is reserved
for SRAM (like the downstream driver stack and compiler). Userspace
doesn't need access to the SRAM.

The h/w has no MMU nor external IOMMU and is a DMA engine which can
read and write anywhere in memory without h/w bounds checks. The user
submitted command streams must be validated against the bounds of the
GEM BOs. This is similar to the VC4 design which validates shaders.

The job submit is based on the rocket driver for the Rockchip NPU
utilizing the GPU scheduler. It is simpler as there's only 1 core rather
than 3.

Tested on i.MX93 platform (U65) and FVP (U85) with Mesa Teflon
support.

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Tomeu Vizoso <tomeu@tomeuvizoso.net>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20251020-ethos-v6-2-ecebc383c4b7@kernel.org
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>

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