util/autoport: Fix VGA register warning

The warning is printed using Printf syntax but actually Println is used
resulting in printing the format string first and the arguments second:
"%s. (%s) Default:%s WARNING: [...]"

Change-Id: I411fc47832dd7a82752f233c4909b98190340ccb
Signed-off-by: Maximilian Schander <coreboot@mimoja.de>
Reviewed-on: https://review.coreboot.org/22352
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

util/autoport/log_maker.go

@@ -51,7 +51,8 @@ const MAXPROMPTRETRY = 3
 
 func PromptUser(prompt string, opts []string) (match string, err error) {
 	for i := 1; i < MAXPROMPTRETRY; i++ {
-		fmt.Println("%s. (%s) Default:%s", prompt, strings.Join(opts, "/"), opts[0])
+		fmt.Printf("%s. (%s) Default:%s\n", prompt,
+		           strings.Join(opts, "/"), opts[0])
 		var usrInput string
 		fmt.Scanln(&usrInput)