x86: Merge io.h

io_32.h and io_64.h are now identical.  Merge them into io.h.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1265380629-3212-8-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>