metag: checksum.h: fix carry in csum_tcpudp_nofold

In csum_tcpudp_nofold, add 1 if the carry bit is set after adding the
destination IP address (32 bits) to the checksum (16 bits).

The lack of carry handling for this particular addition meant that a
destination address of *.*.255.255 (e.g. certain broadcasts) sometimes
resulted in an incorrect checksum. This bug has been present in the Meta
port since the code was written in the 2.4 days.
Reported-by: Marcin Nowakowski <Marcin.Nowakowski@pure.com>
Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/metag/include/asm/checksum.h

@@ -64,7 +64,8 @@ static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
 					__wsum sum)
 {
 	unsigned long len_proto = (proto + len) << 8;
-	asm ("ADD    %0, %0, %1\n"
+	asm ("ADDS   %0, %0, %1\n"
+	     "ADDCS  %0, %0, #1\n"
 	     "ADDS   %0, %0, %2\n"
 	     "ADDCS  %0, %0, #1\n"
 	     "ADDS   %0, %0, %3\n"