cpufreq: ppc_cbe: fix possible object reference leak
The call to of_get_cpu_node returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.
Detected by coccinelle with the following warnings:
./drivers/cpufreq/ppc_cbe_cpufreq.c:89:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 76, but without a corresponding object release within this function.
./drivers/cpufreq/ppc_cbe_cpufreq.c:89:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 76, but without a corresponding object release within this function.