drm/komeda: Update the chip identify

1. Drop komeda-CORE product id comparison and put it into the d71_identify
2. Update pipeline node DT-binding:
   (a). Skip the needless pipeline DT node.
   (b). Return fail if the essential pipeline DT node is missing.

With these changes, for chips in same family no need to change the DT.

v2: Rebase
v3: Address Mihail's comments.

Signed-off-by: james qian wang (Arm Technology China) <james.qian.wang@arm.com>
Reviewed-by: Mihail Atanassov <mihail.atanassov@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191210084828.19664-2-james.qian.wang@arm.com