Optee a80 porting

Optee-os add a80 platform support.

This request have three patchs, The patchs summary:
1.gic driver add gic_cpu_init function, mainly for secondary cpu secure stage initialization,
2.Make uart driver more portable, add common console.h and console basic functions,
3.Add plat-sunxi support, the initial version, running on A80 Optimus board.

All patchs only tested on A80 Optimus board, Due to the lack of platform.
Mayeb the uart driver patch should be test on vexpress platform.
This isn't very friendly, to be able to understand this value you need to go into the ref man and look it up. Since it's only configured once I guess a comment describing what kind of access is enabled with this should be enough.