cpufreq: imx6q: add return value check for voltage scale

[ Upstream commit 6ef28a04d1ccf718eee069b72132ce4aa1e52ab9 ]

Add return value check for voltage scale when ARM clock
rate change fail.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>