ARM: bcm: Fix refcount leak in bcm_kona_smc_init

of_find_matching_node() returns a node pointer with refcount
incremented, we should use of_node_put() on it when not need anymore.
Add missing of_node_put() to avoid refcount leak.

Fixes: b8eb35fd ("ARM: bcm281xx: Add L2 cache enable code")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>