ARM: shmobile: apmu: silence build warnings

With shmobile_defconfig but SMP=n && SUSPEND=n, I get:

arch/arm/mach-shmobile/platsmp-apmu.c:49:12: warning: 'apmu_power_off' defined but not used [-Wunused-function]
arch/arm/mach-shmobile/platsmp-apmu.c:70:12: warning: 'apmu_wrap' defined but not used [-Wunused-function]

Annotate those functions like the functions around it.
Signed-off-by: NWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

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

@@ -46,7 +46,7 @@ static int __maybe_unused apmu_power_on(void __iomem *p, int bit)
 	return 0;
 }
 
-static int apmu_power_off(void __iomem *p, int bit)
+static int __maybe_unused apmu_power_off(void __iomem *p, int bit)
 {
 	/* request Core Standby for next WFI */
 	writel_relaxed(3, p + CPUNCR_OFFS(bit));
@@ -67,7 +67,7 @@ static int __maybe_unused apmu_power_off_poll(void __iomem *p, int bit)
 	return 0;
 }
 
-static int apmu_wrap(int cpu, int (*fn)(void __iomem *p, int cpu))
+static int __maybe_unused apmu_wrap(int cpu, int (*fn)(void __iomem *p, int cpu))
 {
 	void __iomem *p = apmu_cpus[cpu].iomem;