[ARM] Add Cortex A7 support

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
[ARM] generic: Add Sun7i SOC support

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
[DOCS] Sun7i: add Cubieboard2 preliminary documentation.

This is not complete yet but it gives few hints.
In particular, how to get a PSCI enabled u-boot.

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
[DOCS] Sun7i: add intructions to allow autoboot of Xvisor.

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>
Merge remote-tracking branch 'upstream/master' into A20

Signed-off-by: Jean-Christophe DUBOIS <jcd@tribudubois.net>

Conflicts:
	arch/arm/board/generic/dts/sun7i/objects.mk
	arch/arm/cpu/common/include/arm_features.h
	docs/arm/sun7i-cubieboard2.txt