cpufreq: s5pv210: Defer probe if getting regulators fail

There is possibility, that when probing driver, regulators are not yet
initialized. In this case we should return EPROBE_DEFER and wait till
they're initialized, since they're required currently for cpufreq driver
to work. Also move regulator initialization code at beginning of probe,
so we can defer as fast as posibble.

Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>