[CI][ETHOSN] Enable CI for Ethos-N (#6171)

[CI][ETHOSN] Enable CI for Ethos-N (#6171)

This introduces the necessary changes to docker to
support building the Ethos-N driver stack. This is
required for subsequent patches which introduce
the Ethos-N integration into TVM.

Co-authored-by: Leo Blonk <Leo.Blonk@arm.com>
Co-authored-by: Leandro Nunes <leandro.nunes@arm.com>
# Please enter the commit message for your changes. Lines starting
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# Date:      Mon Jul 27 15:43:41 2020 +0100
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# On branch ethosn-ci
# Changes to be committed:
#	modified:   docker/Dockerfile.ci_cpu
#	new file:   docker/install/ubuntu_install_ethosn_driver_stack.sh
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# Untracked files:
#	CombinedMemoryMap.hex
#	OutputModel.hex
#	config.txt
#	docker/install/ethosn_cap/
#	docker/install/ethosn_driver_dev-20.05-dbg-20200612-141030.tar.gz
#	ssd.npy
#	tests/python/integration/test_tir_gemm.py
#	tests/python/relay/test_pattern_annotate.py
#	tests/python/unittest/failure.py
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