Correct SPL uses of USB_KEYBOARD

This converts 2 usages of this option to the non-SPL form, since there is
no SPL_USB_KEYBOARD defined in Kconfig

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/coreboot/coreboot.c

@@ -77,7 +77,7 @@ static void board_final_init(void)
 int last_stage_init(void)
 {
 	/* start usb so that usb keyboard can be used as input device */
-	if (CONFIG_IS_ENABLED(USB_KEYBOARD))
+	if (IS_ENABLED(CONFIG_USB_KEYBOARD))
 		usb_init();
 
 	board_final_init();

arch/x86/cpu/efi/payload.c

@@ -171,7 +171,7 @@ int reserve_arch(void)
 int last_stage_init(void)
 {
 	/* start usb so that usb keyboard can be used as input device */
-	if (CONFIG_IS_ENABLED(USB_KEYBOARD))
+	if (IS_ENABLED(CONFIG_USB_KEYBOARD))
 		usb_init();
 
 	return 0;