slimbus: core: Fix mismatch in of_node_get/put

Adding missing corresponding of_node_put

Fixes: 7588a511

 ("slimbus: core: add support to device tree helper")
Signed-off-by: Saravana Kannan <saravanak@google.com>
[Srini: added fixes tag, removed NULL check and updated log]
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20200511151334.362-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>