cpufreq: Fix a typo in comment

Fix a typo in a comment in cpufreq_governor.h.

[rjw: Changelog]
Signed-off-by: Namhyung Kim <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/cpufreq/cpufreq_governor.h

···
  * dbs: used as a shortform for demand based switching It helps to keep variable
  *	names smaller, simpler
  * cdbs: common dbs
- * on_*: On-demand governor
+ * od_*: On-demand governor
  * cs_*: Conservative governor
  */