of: property: Delete of_devlink kernel commandline option

With the addition of fw_devlink kernel commandline option, of_devlink is
redundant and not useful anymore. So, delete it.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Saravana Kannan <saravanak@google.com>
Link: https://lore.kernel.org/r/20200222014038.180923-6-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>