USB: make transfer_buffer_lengths in struct urb field u32

Roel Kluin pointed out that transfer_buffer_lengths in struct urb was
declared as an 'int'.  This patch changes this field to be 'u32' to
prevent any potential negative conversion and comparison errors.

This triggered a few compiler warning messages when these fields were
being used with the min macro, so they have also been fixed up in this
patch.

Cc: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/r8a66597-hcd.c b/drivers/usb/host/r8a66597-hcd.c
index 5e942d9..713f4cf 100644
--- a/drivers/usb/host/r8a66597-hcd.c
+++ b/drivers/usb/host/r8a66597-hcd.c
@@ -1394,7 +1394,7 @@
 			   (int)urb->iso_frame_desc[td->iso_cnt].length);
 	} else {
 		buf = (u16 *)(urb->transfer_buffer + urb->actual_length);
-		size = min((int)bufsize,
+		size = min_t(u32, bufsize,
 			   urb->transfer_buffer_length - urb->actual_length);
 	}