dt-bindings: qcom_nandc: fix the ipq806x device tree example

1. Correct the compatible string for IPQ806x
2. Change the NAND controller and NAND chip nodes name
   for more clarity.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>