Spelling fixes

Spelling errors found using github.com/lucasdemarchi/codespell
A tool to fix common misspellings.
This tool is licensed under GNU General Public License, version 2.

Change-Id: I8af789c1e0fef9938baced40315b525199636601
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/power-supply/record_manager.hpp b/power-supply/record_manager.hpp
index 8504803..53e5b9b 100644
--- a/power-supply/record_manager.hpp
+++ b/power-supply/record_manager.hpp
@@ -42,7 +42,7 @@
  * The history is the average and maximum power values across 30s
  * intervals.  Every 30s, a new record will be available from the
  * PS.  This class takes that raw PS data and converts it into
- * something useable by D-Bus.  It ensures the readings are always
+ * something usable by D-Bus.  It ensures the readings are always
  * sorted newest to oldest, and prunes out the oldest entries when
  * necessary.  If there is a problem with the ordering IDs coming
  * from the PS, it will clear out the old records and start over.