nvramcui: Use regular `if` over `#if` for `IS_ENABLED`

When using the regular `if` construct, the compiler will check the
guarded code independently from the condition.

Change-Id: I988fa9379e8c748013a67ef29fa908b4d9a970ad
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/18794
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/nvramcui/nvramcui.c

@@ -176,9 +176,8 @@ int main(void)
 	int ch, done;
 	int i;
 
-#if IS_ENABLED(CONFIG_LP_USB)
-	usb_initialize();
-#endif
+	if (IS_ENABLED(CONFIG_LP_USB))
+		usb_initialize();
 
 	/* coreboot data structures */
 	lib_get_sysinfo();