This patch adds an idle member to the ppc_md structure and calls it from
cpu_idle().  If a platform leaves ppc_md.idle as null it will get the default
idle loop default_idle().
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>