cpufreq: armada-37xx: Fix clock leak

There was no clk_put() balancing the clk_get(). This commit fixes it.

Fixes: 92ce45fb (cpufreq: Add DVFS support for Armada 37xx)
Cc: 4.16+ <stable@vger.kernel.org> # 4.16+
Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>