usb: musb: gadget: fix to_musb_request() to not return NULL

The gadget function drivers should ensure the usb_request parameter
passed in is not NULL. UDC core doesn't check if it is NULL, so MUSB
driver shouldn't have to check it either.

Convert to_musb_request() to a simple macro to not directly return NULL
to avoid warnings from code static analysis tools.
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/musb_gadget.h

@@ -60,10 +60,7 @@ struct musb_request {
 	enum buffer_map_state map_state;
 };
 
-static inline struct musb_request *to_musb_request(struct usb_request *req)
-{
-	return req ? container_of(req, struct musb_request, request) : NULL;
-}
+#define to_musb_request(r)	container_of((r), struct musb_request, request)
 
 extern struct usb_request *
 musb_alloc_request(struct usb_ep *ep, gfp_t gfp_flags);