bootloader: fix signatures_ok usage in usb.c after refactoring

bootloader/usb.c

@@ -444,7 +444,7 @@ static void hid_rx_callback(usbd_device *dev, uint8_t ep)
 			}
 			if (brand_new_firmware || button.YesUp) {
 				// check whether current firmware is signed
-				if (signatures_ok(NULL)) {
+				if (SIG_OK == signatures_ok(NULL)) {
 					old_was_unsigned = false;
 					// backup metadata
 					backup_metadata(meta_backup);
@@ -603,7 +603,7 @@ static void hid_rx_callback(usbd_device *dev, uint8_t ep)
 		// 1) old firmware was unsigned
 		// 2) firmware restore flag isn't set
 		// 3) signatures are not ok
-		if (old_was_unsigned || (flags & 0x01) == 0 || !signatures_ok(NULL)) {
+		if (old_was_unsigned || (flags & 0x01) == 0 || SIG_OK != signatures_ok(NULL)) {
 			memzero(meta_backup, sizeof(meta_backup));
 		}
 		// copy new firmware header