util/arm_einj.py: add an utility for ARM error injection via QEMU

util/arm_einj.py: add an utility for ARM error injection via QEMU

Testing rasdaemon is not easy, as it depends on either having
real hardware producing events or a test BIOS. This is usually
not available and/or not too reliable.

So, take a different approach by adding a QEMU QAPI designed for
doing hardware error injection. The QEMU patches are at:

	https://gitlab.com/mchehab_kernel/qemu/-/tree/arm-error-inject-v2

And some instructions about how to use it are at rasdaemon wiki
pages at github:

	https://github.com/mchehab/rasdaemon/wiki

Add the error injection tool to rasdaemon sources.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>