dev_dbg: check dev_dbg() arguments

Duplicate what Zach Brown did for pr_debug in commit
8b2a1fd1b394c60eaa2587716102dd5e9b4e5990

[akpm@linux-foundation.org: fix a couple of things which broke]
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index b89a98e..7a60285 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -119,8 +119,7 @@
 		"first one fails");
 
 
-#ifdef	DEBUG
-static inline char *portspeed (int portstatus)
+static inline char *portspeed(int portstatus)
 {
 	if (portstatus & (1 << USB_PORT_FEAT_HIGHSPEED))
     		return "480 Mb/s";
@@ -129,7 +128,6 @@
 	else
 		return "12 Mb/s";
 }
-#endif
 
 /* Note that hdev or one of its children must be locked! */
 static inline struct usb_hub *hdev_to_hub(struct usb_device *hdev)