smp: Micro-optimize smp_call_function_many_cond()

Call the generic send_call_function_single_ipi() function, which
will avoid the IPI when @last_cpu is idle.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/smp.c

@@ -694,7 +694,7 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
 		 * provided mask.
 		 */
 		if (nr_cpus == 1)
-			arch_send_call_function_single_ipi(last_cpu);
+			send_call_function_single_ipi(last_cpu);
 		else if (likely(nr_cpus > 1))
 			arch_send_call_function_ipi_mask(cfd->cpumask_ipi);
 	}