ARM: configs: Enable cpufreq-cpu0 for multi_v7_defconfig

Many boards share the cpufreq-cpu0 driver meaning that if we enable it in
multi_v7_defconfig we can get a reasonable amount of functional utility for
systems and test coverage for a fairly small increase in kernel size.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>