cpufreq: Move gov_attr_* macros to cpufreq.h

cpufreq: Move gov_attr_* macros to cpufreq.h

These macros can be reused by governors which don't use the common
governor code present in cpufreq_governor.c and should be moved to the
relevant header.

Now that they are getting moved to the right header file, reuse them in
schedutil governor as well (that required rename of show/store
routines).

Also create gov_attr_wo() macro for write-only sysfs files, this will be
used by Interactive governor in a later patch.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>