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: Id20fef954fd977a307ba36dce5c8c7365aa96a6d
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/lib/gen_valid.py b/lib/gen_valid.py
index f453689..674ea2e 100755
--- a/lib/gen_valid.py
+++ b/lib/gen_valid.py
@@ -29,7 +29,7 @@
 def get_var_name(var_name):
     r"""
     If var_name has a value, simply return it.  Otherwise, get the variable
-    name of the first arguement used to call the validation function (e.g.
+    name of the first argument used to call the validation function (e.g.
     valid_value, valid_integer, etc.) and return it.
 
     This function is designed solely for use by other functions in this file.