drivers: core: fw_devlink: Make the error message a bit more useful

It would make it easier to debugs issues similar to the ones
reported[1][2] recently where some devices didn't have the fwnode set.

[1] - https://lore.kernel.org/all/7b995947-4540-4b17-872e-e107adca4598@notapiano/
[2] - https://lore.kernel.org/all/20240910130019.35081-1-jonathanh@nvidia.com/



Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20241024061347.1771063-4-saravanak@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>