sparc: Make SPARC use the new is_idle_task() API

Change from direct comparison of ->pid with zero to is_idle_task().
Signed-off-by: NPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>

arch/sparc/kernel/setup_32.c

@@ -84,7 +84,7 @@ static void prom_sync_me(void)
 
 	prom_printf("PROM SYNC COMMAND...\n");
 	show_free_areas(0);
-	if(current->pid != 0) {
+	if (!is_idle_task(current)) {
 		local_irq_enable();
 		sys_sync();
 		local_irq_disable();