CONFIG_GENERIC_CPUFREQ_CPU0 disappeared with commit bbcf0719
("cpufreq: cpu0: rename driver and internals to 'cpufreq_dt'") and some
defconfigs are still using it instead of the new one.

Use the renamed CONFIG_CPUFREQ_DT generic driver.

Cc: <stable@vger.kernel.org>        # 3.18
Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Kevin Hilman <khilman@linaro.org>