dscc4: Undefined signed int shift

My analysis in the below mail applies, although the second part is
unnecessary because i isn't used in arithmetic operations here:

https://marc.info/?l=openbsd-tech&m=145377854103866&w=2

Thanks for your time.
Signed-off-by: Michael McConville <mmcco@mykolab.com>
Acked-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/dscc4.c

@@ -1626,7 +1626,7 @@ static void dscc4_tx_irq(struct dscc4_pci_priv *ppriv,
 		if (state & Xpr) {
 			void __iomem *scc_addr;
 			unsigned long ring;
-			int i;
+			unsigned int i;
 
 			/*
 			 * - the busy condition happens (sometimes);