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>

drivers/usb/host/sl811-hcd.c

@@ -230,7 +230,7 @@ static void in_packet(
 	writeb(usb_pipedevice(urb->pipe), data_reg);
 
 	sl811_write(sl811, bank + SL11H_HOSTCTLREG, control);
-	ep->length = min((int)len,
+	ep->length = min_t(u32, len,
 			urb->transfer_buffer_length - urb->actual_length);
 	PACKET("IN%s/%d qh%p len%d\n", ep->nak_count ? "/retry" : "",
 			!!usb_gettoggle(urb->dev, ep->epnum, 0), ep, len);
@@ -255,7 +255,7 @@ static void out_packet(
 	buf = urb->transfer_buffer + urb->actual_length;
 	prefetch(buf);
 
-	len = min((int)ep->maxpacket,
+	len = min_t(u32, ep->maxpacket,
 			urb->transfer_buffer_length - urb->actual_length);
 
 	if (!(control & SL11H_HCTLMASK_ISOCH)