powerpc: Make ppc_md.{halt, restart} __noreturn

powernv marks it's halt and restart calls as __noreturn. However,
ppc_md does not have this annotation. Add the annotation to ppc_md,
and then to every halt/restart function that is missing it.

Additionally, I have verified that all of these functions do not
return. Occasionally I have added a spin loop to be sure.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pasemi/setup.c

@@ -62,7 +62,7 @@ static int num_mce_regs;
 static int nmi_virq = NO_IRQ;
 
 
-static void pas_restart(char *cmd)
+static void __noreturn pas_restart(char *cmd)
 {
 	/* Need to put others cpu in hold loop so they're not sleeping */
 	smp_send_stop();