cpufreq: SCPI: Depend on SCPI clk driver

The SCPI clk driver registers the virtual cpufreq device that kicks off
initialisation of the SCPI cpufreq driver. Also, clk_get() will fail for
the cpufreq driver if the SCPI clk driver is missing.

Fix this by making the SCPI cpufreq driver explicitly depend on the SCPI
clk driver.

Fixes: 8def3103 (cpufreq: arm_big_little: add SCPI interface driver)
Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>