arm64: fix up obsolete cpu function usage.

Thanks to spatch.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org

arch/arm64/kernel/smp.c

@@ -635,7 +635,7 @@ void smp_send_stop(void)
 		cpumask_t mask;
 
 		cpumask_copy(&mask, cpu_online_mask);
-		cpu_clear(smp_processor_id(), mask);
+		cpumask_clear_cpu(smp_processor_id(), &mask);
 
 		smp_cross_call(&mask, IPI_CPU_STOP);
 	}