reset: hi6220: Add support for AO reset controller

This is required to bring Mali450 gpu out of reset.

Cc: Peter Griffin <peter.griffin@linaro.org>
Cc: Enrico Weigelt <info@metux.net>
Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
[jstultz: Added comment, Fix void return build issue
Reported-by: kbuild test robot <lkp@intel.com&gt;]>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>