cpufreq: pmac32: fix possible object reference leak

The call to of_find_node_by_name 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/pmac32-cpufreq.c:557:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 552, but without a corresponding object release within this function.
./drivers/cpufreq/pmac32-cpufreq.c:569:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 552, but without a corresponding object release within this function.
./drivers/cpufreq/pmac32-cpufreq.c:598:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 587, but without a corresponding object release within this function.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-pm@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

drivers/cpufreq/pmac32-cpufreq.c

@@ -552,6 +552,7 @@ static int pmac_cpufreq_init_7447A(struct device_node *cpunode)
 	volt_gpio_np = of_find_node_by_name(NULL, "cpu-vcore-select");
 	if (volt_gpio_np)
 		voltage_gpio = read_gpio(volt_gpio_np);
+	of_node_put(volt_gpio_np);
 	if (!voltage_gpio){
 		pr_err("missing cpu-vcore-select gpio\n");
 		return 1;
@@ -588,6 +589,7 @@ static int pmac_cpufreq_init_750FX(struct device_node *cpunode)
 	if (volt_gpio_np)
 		voltage_gpio = read_gpio(volt_gpio_np);
 
+	of_node_put(volt_gpio_np);
 	pvr = mfspr(SPRN_PVR);
 	has_cpu_l2lve = !((pvr & 0xf00) == 0x100);