Fix common misspellings

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index b03771d..2dafc5c 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1782,7 +1782,7 @@
  *	cpufreq_update_policy - re-evaluate an existing cpufreq policy
  *	@cpu: CPU which shall be re-evaluated
  *
- *	Usefull for policy notifiers which have different necessities
+ *	Useful for policy notifiers which have different necessities
  *	at different times.
  */
 int cpufreq_update_policy(unsigned int cpu)