cpufreq: ap806: fix possible object reference leak

cpufreq: ap806: fix possible object reference leak

The call to of_find_compatible_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/armada-8k-cpufreq.c:187:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 130, but without a corresponding object release within this function.
./drivers/cpufreq/armada-8k-cpufreq.c:191:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 130, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Gregory Clement <gregory.clement@bootlin.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-pm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>