of: property: fw_devlink: Fixup behaviour when 'node_not_dev' is set

In the struct supplier_bindings the member 'node_not_dev' is described as
"The consumer node containing the property is never a device.", but that is
inconsistent with the behaviour of the code in of_link_property(), as it
calls of_get_compat_node() that starts parsing for a compatible property
from the node it gets passed to it. The proper behaviour is to start at the
node's parent, so let's do that.

While at it, let's take the opportunity to update the description of the
'node_not_dev' flag, as to clarify its purpose.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210902090221.820254-1-ulf.hansson@linaro.org