cpufreq: scpi: fix error return code in scpi_cpufreq_init()

Fix to return a negative error code from the clk_get() error handling
case instead of 0, as done elsewhere in this function.

Fixes: 343a8d17 (cpufreq: scpi: remove arm_big_little dependency)
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>