[POWERPC] Fix __raw* accessors

The new IO accessor code allows to stick a token in the top bit of MMIO
addresses which gets masked out during actual accesses. However, the
__raw_* accessors forgot to mask it out. This fixes it.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>