1. Add detailed layer/layer_state definitions
2. Add d71_layer_init to report layer features and capabilities according
   to D71 layer block.
3. Add d71_layer_updat/disable

v2: Rebase.
Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
[removed d71_layer_dump() from this commit]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>