of: property: Minor style clean up of of_link_to_phandle()

Adding a debug log instead of silently ignoring a phandle for an early
device. Also, return the right error code instead of 0 even though the
actual execution flow won't change.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191105065000.50407-2-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>