Updates for ARM Trusted Firmware tag v1.0

* New load address for plat-vexpress,fvp
* Entry vector extended with system_off and system_reset
  entries
Add documentation for ARM Trusted Firmware

Adds documentation how to compile and run with
ARM Trusted Firmware.
MMU: Simplify tee_mmu_switch function

Replaced direct CP15 instructions with macros instead and removed some
unnecessary code.