modinfo: Use ,, for lowercasing instead of tr in a subshell.

completions/modinfo

@@ -9,7 +9,7 @@ _modinfo()
         -F|--field)
             COMPREPLY=( $( compgen -W 'alias author depends description
                 filename firmware license parm srcversion staging vermagic
-                version' -- "$(echo "$cur" | tr '[:upper:]' '[:lower:]')" ) )
+                version' -- "${cur,,}" ) )
             return
             ;;
         -k)