cpufreq: arm-big-little: use clk_get instead of clk_get_sys

Currently clk_get_sys is used with cpu-cluster.<n> as the device id
which is incorrect. It should be connection/consumer ID instead.

It is possible to specify input clock in the cpu device node along
with the optional clock-name. clk_get_sys can't handle that.

This patch replaces clk_get_sys with clk_get to extend support for
clocks specified in the device tree cpu node.

Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>