drm/komeda: Add debugfs node "register" for register dump

Add a debugfs node "register" and entry function dump_register to
dev/pipeline/component to register dump, then user can read
"/sys/kernel/debug/komeda/register" to get the register values via these
chip function.

Signed-off-by: James Qian Wang (Arm Technology China) <james.qian.wang@arm.com>
[Added the d71_layer_dump() function that was in a previous commit]
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>