usb: gadget: mass_storage: remove >= 0 check for unsigned type

| In file included from drivers/usb/gadget/acm_ms.c:43:
| f_mass_storage.c:2199:18: warning: comparison of unsigned expression >= 0 is always true  [-Wtautological-compare]
|         if (common->lun >= 0 && common->lun < common->nluns)
|             ~~~~~~~~~~~ ^  ~

common->lun is defined as "unsigned int" so its value is always >= 0.
It is assigned via cbw->Lun which is defined as u8 so it is also not
abused as -1.

[ mina86@mina86.com : make lun unsigned int and use %u in DBG() macro for it ]
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_mass_storage.c

@@ -1691,7 +1691,7 @@ static int check_command(struct fsg_common *common, int cmnd_size,
 			 int needs_medium, const char *name)
 {
 	int			i;
-	int			lun = common->cmnd[1] >> 5;
+	unsigned int		lun = common->cmnd[1] >> 5;
 	static const char	dirletter[4] = {'u', 'o', 'i', 'n'};
 	char			hdlen[20];
 	struct fsg_lun		*curlun;
@@ -1757,7 +1757,7 @@ static int check_command(struct fsg_common *common, int cmnd_size,
 
 	/* Check that the LUN values are consistent */
 	if (common->lun != lun)
-		DBG(common, "using LUN %d from CBW, not LUN %d from CDB\n",
+		DBG(common, "using LUN %u from CBW, not LUN %u from CDB\n",
 		    common->lun, lun);
 
 	/* Check the LUN */
@@ -1777,7 +1777,7 @@ static int check_command(struct fsg_common *common, int cmnd_size,
 		 */
 		if (common->cmnd[0] != INQUIRY &&
 		    common->cmnd[0] != REQUEST_SENSE) {
-			DBG(common, "unsupported LUN %d\n", common->lun);
+			DBG(common, "unsupported LUN %u\n", common->lun);
 			return -EINVAL;
 		}
 	}
@@ -2169,7 +2169,7 @@ static int received_cbw(struct fsg_dev *fsg, struct fsg_buffhd *bh)
 	if (common->data_size == 0)
 		common->data_dir = DATA_DIR_NONE;
 	common->lun = cbw->Lun;
-	if (common->lun >= 0 && common->lun < common->nluns)
+	if (common->lun < common->nluns)
 		common->curlun = &common->luns[common->lun];
 	else
 		common->curlun = NULL;