[PowerPC64LE] Use correct in_masks table on LE to fix checksumming

Due to a check that should have been an endian check being an #if 0,
the wrong checksum mask table was being used on LE, which was causing
extreme strangeness in DNS resolution -- *some* hosts would be resolvable,
but most would not.

This fixes DNS resolution.

(I am committing some parts of the LE patchset ahead of time to reduce the
amount of work I have to do while committing the main patchset.)

Sponsored by:	Tag1 Consulting, Inc.

sys/powerpc/powerpc/in_cksum.c

@@ -42,6 +42,7 @@
 
 #include <sys/cdefs.h>			/* RCS ID & Copyright macro defns */
 
+#include <sys/endian.h>
 #include <sys/param.h>
 #include <sys/mbuf.h>
 #include <sys/systm.h>
@@ -73,7 +74,7 @@
     }
 
 static const u_int32_t in_masks[] = {
-#if 0
+#if _BYTE_ORDER == _LITTLE_ENDIAN
 	/*0 bytes*/ /*1 byte*/	/*2 bytes*/ /*3 bytes*/
 	0x00000000, 0x000000FF, 0x0000FFFF, 0x00FFFFFF,	/* offset 0 */
 	0x00000000, 0x0000FF00, 0x00FFFF00, 0xFFFFFF00,	/* offset 1 */