[PATCH] headers: enable ppc64 ___arch__swab16 and ___arch__swab32

This patch cleans up asm-ppc64/byteorder.h to enable ___arch__swab16 and
___arch__swab32 which are marked TODO currently.  It removes ___arch__swab64
because ppc64 does not have short instruction combinations for swab64, the
recent gcc generates enough smart code that is equivalent to hand assembled
code under my tests.

Signed-off-by: GOTO Masanori <gotom@debian.or.jp>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>