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.
Linux kernel currently have used 8 IPI now.
enum ipi_msg_type {
	IPI_WAKEUP,
	IPI_TIMER,
	IPI_RESCHEDULE,
	IPI_CALL_FUNC,
	IPI_CALL_FUNC_SINGLE,
	IPI_CPU_STOP,
	IPI_COMPLETION,
	IPI_CPU_BACKTRACE,
};
ID0-ID7 have been consumed. 
ARM GIC Arch have the recommendation, I will follow this recommendation.
write32(0xffffffff, gic.gicd_base + GICD_IGROUPR(0));
will change to 
write32(0xffff00ff, gic.gicd_base + GICD_IGROUPR(0));