cpufreq: qcom-hw: Use devm_platform_ioremap_resource() to simplify code

devm_platform_ioremap_resource() is the combination of
platform_get_resource() and devm_ioremap_resource(). Hence, use it to
simplify the code a bit.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>