PM / devfreq: kernel-doc typo corrections

Parameter documentation needs a ':' for scripts/kernel-doc
to parse properly.

Minor fixes for ones warned by:
./scripts/kernel-doc -text drivers/devfreq/devfreq.c>/dev/null

Signed-off-by: Nishanth Menon <nm@ti.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>