ARM: shmobile: smp: Make shmobile_smp_apmu_cpu_shutdown() static

shmobile_smp_apmu_cpu_shutdown() is used inside platsmp-apmu.c only.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm/mach-shmobile/platsmp-apmu.c

@@ -170,7 +170,7 @@ static inline void cpu_enter_lowpower_a15(void)
 	dsb();
 }
 
-void shmobile_smp_apmu_cpu_shutdown(unsigned int cpu)
+static void shmobile_smp_apmu_cpu_shutdown(unsigned int cpu)
 {
 
 	/* Select next sleep mode using the APMU */