[CPUFREQ] cpufreq.h: Fix some checkpatch.pl coding style issues.

Before:
$ scripts/checkpatch.pl --file --terse include/linux/cpufreq.h
total: 14 errors, 11 warnings, 419 lines checked

After:
$ scripts/checkpatch.pl --file --terse include/linux/cpufreq.h
total: 2 errors, 4 warnings, 422 lines checked

Signed-off-by: Thiago Farina <tfransosi@gmail.com>
Signed-off-by: Dave Jones <davej@redhat.com>