This patch adds "frequency table helpers" to kernel/cpufreq.c and
updates some drivers to use them.

Most CPU frequency scaling methods only support a few static
frequencies. In these drivers a lot of duplicated code existed in the
->setpolicy and ->verify calls.

Please note that this in no way changes the behaviour of cpufreq or of
the ->setpolicy or ->verify calls. These "frequency table helpers"
aren't for drivers which either only support policies (longrun) or
really many frequency states (ARM, gx-suspmod).