[PATCH] ppc: Make ARCH=ppc build again with new syscall path

This makes ARCH=ppc build in your powerpc tree again, with the new
syscall entry/exit path.

Still doesn't actually boot on my Pegasos; the last thing I see is
'MMU:exit'. But at least it builds -- I'll look at why it doesn't boot
later, so that I can see if the mv643xx_eth actually works with ARCH=ppc
(it doesn't with ARCH=powerpc; two in every three packets I receive are
offset by 4 bytes).

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>