USB: message: cleanup min_t() cast in usb_sg_init()

"length" is type size_t so the cast to unsigned int truncates the
upper bytes.  This isn't an issue in real life (I've checked the
callers) but it's a bit messy.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/core/message.c

@@ -435,7 +435,7 @@ int usb_sg_init(struct usb_sg_request *io, struct usb_device *dev,
 
 			len = sg->length;
 			if (length) {
-				len = min_t(unsigned, len, length);
+				len = min_t(size_t, len, length);
 				length -= len;
 				if (length == 0)
 					io->entries = i + 1;