cpufreq: mt8173: remove redundant regulator_get_voltage() call

Remove redundant regulator_get_voltage() call to get Vsram value
since it will be obtained later at the beginning of voltage tracking
loop.

Signed-off-by: Pi-Cheng Chen <pi-cheng.chen@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>