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.
The ARM GIC Arch spec says:
*In any system that implements the ARM Security Extensions, to support a consistent model for message passing
between processors, ARM strongly recommends that all processors reserve:
• ID0-ID7 for Non-secure interrupts
• ID8-ID15 for Secure interrupts.*

We should follow that recommendation unless we have a good reason not to.