The current implementation of the scmi_cpufreq_init() function returns
-EPROBE_DEFER when the OPP table is not populated. In practice the
cpufreq core cannot handle this error code.
Therefore, fix the return value and clarify the error message.

Link: https://lore.kernel.org/r/20210218222326.15788-2-nicola.mazzucato@arm.comAcked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Nicola Mazzucato <nicola.mazzucato@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>