cpufreq: dt: dev_pm_opp_of_cpumask_add_table() may return -EPROBE_DEFER

The function dev_pm_opp_of_cpumask_add_table() may return -EPROBE_DEFER,
which needs to be propagated to the caller to try probing the driver
later on.

Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
[ Viresh: Massage changelog/subject, improve code. ]
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>