usb: storage: Add usb_stor_dbg, reduce object size

Reduce the size of the objects by consolidating
the duplicated USB_STORAGE into a single function.

Add function usb_stor_dbg to emit debugging messages.
Always validate the format and arguments.
Reduce the number of uses of CONFIG_USB_STORAGE_DEBUG.

Reduces size of objects ~7KB when CONFIG_USB_STORAGE_DEBUG
is set.

$ size drivers/usb/storage/built-in.o*
   text	   data	    bss	    dec	    hex	filename
 140133	  55296	  70312	 265741	  40e0d	drivers/usb/storage/built-in.o.new
 147494	  55248	  70296	 273038	  42a8e	drivers/usb/storage/built-in.o.old

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/storage/debug.h b/drivers/usb/storage/debug.h
index dbb985d..d4280e1 100644
--- a/drivers/usb/storage/debug.h
+++ b/drivers/usb/storage/debug.h
@@ -50,12 +50,16 @@
 void usb_stor_show_command(struct scsi_cmnd *srb);
 void usb_stor_show_sense( unsigned char key,
 		unsigned char asc, unsigned char ascq );
-#define US_DEBUGP(x...) printk( KERN_DEBUG USB_STORAGE x )
-#define US_DEBUGPX(x...) printk( x )
-#define US_DEBUG(x) x 
+__printf(1, 2) int usb_stor_dbg(const char *fmt, ...);
+
+#define US_DEBUGP(fmt, ...)	usb_stor_dbg(fmt, ##__VA_ARGS__)
+#define US_DEBUGPX(fmt, ...)	printk(fmt, ##__VA_ARGS__)
+#define US_DEBUG(x)		x
 #else
-#define US_DEBUGP(x...)
-#define US_DEBUGPX(x...)
+#define US_DEBUGP(fmt, ...)					\
+	do { if (0) printk(fmt, ##__VA_ARGS__); } while (0)
+#define US_DEBUGPX(fmt, ...)					\
+	do { if (0) printk(fmt, ##__VA_ARGS__); } while (0)
 #define US_DEBUG(x)
 #endif