style: set column width to 80 chars

Set the column width to 80 chars in the .clang-format and apply the
change.

Change-Id: I9d375a94f12380d297486f9618bf54d7071a7fd0
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/.clang-format b/.clang-format
index 5a4737c..5ac7bba 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,6 +3,7 @@
 Language: Cpp
 IndentWidth: 8
 UseTab: Always
+ColumnLimit:     80
 BreakBeforeBraces: Linux
 AlwaysBreakBeforeMultilineStrings: true
 AllowShortIfStatementsOnASingleLine: false