lib/checksum.c: fix endianess bug

The new generic checksum code has a small dependency on endianess and
worked only on big-endian systems. I could not find a nice efficient
way to express this, so I added an #ifdef. Using
'result += le16_to_cpu(*buff);' would have worked as well, but
would be slightly less efficient on big-endian systems and IMHO
would not be clearer.

Also fix a bug that prevents this from working on 64-bit machines.
If you have a 64-bit CPU and want to use the generic checksum
code, you should probably do some more optimizations anyway, but
at least the code should not break.

Reported-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

lib/checksum.c

@@ -55,7 +55,11 @@ static unsigned int do_csum(const unsigned char *buff, int len)
 		goto out;
 	odd = 1 & (unsigned long) buff;
 	if (odd) {
+#ifdef __LITTLE_ENDIAN
 		result = *buff;
+#else
+		result += (*buff << 8);
+#endif
 		len--;
 		buff++;
 	}
@@ -71,7 +75,7 @@ static unsigned int do_csum(const unsigned char *buff, int len)
 		if (count) {
 			unsigned long carry = 0;
 			do {
-				unsigned long w = *(unsigned long *) buff;
+				unsigned long w = *(unsigned int *) buff;
 				count--;
 				buff += 4;
 				result += carry;
@@ -87,7 +91,11 @@ static unsigned int do_csum(const unsigned char *buff, int len)
 		}
 	}
 	if (len & 1)
+#ifdef __LITTLE_ENDIAN
+		result += *buff;
+#else
 		result += (*buff << 8);
+#endif
 	result = from32to16(result);
 	if (odd)
 		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);