staging/fwserial: Fix build breakage when !CONFIG_BUG

Use WARN() as intended.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fwserial/dma_fifo.c

@@ -33,10 +33,7 @@
 
 #define FAIL(fifo, condition, format...) ({				\
 	fifo->corrupt = !!(condition);					\
-	if (unlikely(fifo->corrupt)) {					\
-		__WARN_printf(format);					\
-	}								\
-	unlikely(fifo->corrupt);					\
+	WARN(fifo->corrupt, format);					\
 })
 
 /*