feat(rk3576): support rk3576

rk3576 is an Octa-core soc with Cortex-a53/a72 inside.
This patch supports the following functions:
1. basic platform setup
2. power up/off cpus
3. suspend/resume cpus
4. suspend/resume system
5. reset system
6. power off system

Change-Id: I67a019822bd4af13e4a3cdd09cf06202f4922cc4
Signed-off-by: XiaoDong Huang <derrick.huang@rock-chips.com>
diff --git a/docs/plat/rockchip.rst b/docs/plat/rockchip.rst
index 384cd73..016bed7 100644
--- a/docs/plat/rockchip.rst
+++ b/docs/plat/rockchip.rst
@@ -11,6 +11,7 @@
 -  rk3368: Octa-Core Cortex-A53
 -  rk3399: Hexa-Core Cortex-A53/A72
 -  rk3566/rk3568: Quad-Core Cortex-A55
+-  rk3576: Octa-Core Cortex-A53/A72
 -  rk3588: Octa-Core Cortex-A55/A76