[POWERPC] bootwrapper: Add 16-bit I/O, sync(), eieio(), and barrier()

Also, include types.h from io.h, so callers don't have to.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>