[PATCH] powerpc: Merge current.h

This patch merges current.h.  This is a one-big-ifdef merge, but both
versions are so tiny, I think we can live with it.  While we're at it,
we get rid of the fairly pointless redirection through get_current()
in the ppc64 version.

Built and booted on POWER5 LPAR (ARCH=powerpc & ARCH=ppc64).  Built
for 32-bit pmac (ARCH=powerpc & ARCH=ppc).

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>