arm64: Add Juno platform support

[Squashed down several commits from dev repository, reused vexpress
config option -- broonie]

Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
(cherry picked from commit 6c658548ecfae02ab544d55a9b60b823e44eb456)
Signed-off-by: Alex Shi <alex.shi@linaro.org>

Conflicts:
	arch/arm64/boot/dts/Makefile
2 files changed