staging: emxx_udc: Add comment for spinlock_t definition.

The nbu2ss_udc structure is used to perform various usb device operations. It is important to protect the members as they can make system calls. Lock variable of type spinlock_t, is used to provide protection by using various spinlock functions.

In this patch, comment is added for spinlock_t definition, to fix the following checkpatch issue:

CHECK: spinlock_t definition without comment

---
Changes in v2:
-Modified commit message

 drivers/staging/emxx_udc/emxx_udc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 789bfb9..78c08e1 100644
@@ -567,7 +567,7 @@ struct nbu2ss_udc {
 	struct usb_gadget_driver *driver;
 	struct platform_device *pdev;
 	struct device *dev;
-	spinlock_t lock;
+	spinlock_t lock; /* Protects nbu2ss_udc structure fields */
 	struct completion		*pdone;
 
 	enum ep0_state			ep0state;

2.9.3