ARM: scu: provide inline dummy functions when SCU is not present

On platforms such as Cortex-A15 based OMAP5, SCU is not used, however
since much code is shared between Cortex-A9 based OMAP4 (which uses
SCU) and OMAP5, It does help to have inline functions returning error
values when SCU is not present on the platform.

arch/arm/mach-omap2/omap-smp.c which is common between OMAP4 and 5
handles the SCU usage only for OMAP4.

This fixes the following build failure with OMAP5 only build:
arch/arm/mach-omap2/built-in.o: In function `omap4_smp_init_cpus':
arch/arm/mach-omap2/omap-smp.c:185: undefined reference to `scu_get_core_count'
arch/arm/mach-omap2/built-in.o: In function `omap4_smp_prepare_cpus':
arch/arm/mach-omap2/omap-smp.c:211: undefined reference to `scu_enable'

Reported-by: Pekon Gupta <pekon@ti.com>
Reported-by: Vincent Stehlé <v-stehle@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/include/asm/smp_scu.h

@@ -23,10 +23,21 @@ static inline unsigned long scu_a9_get_base(void)
 	return pa;
 }
 
+#ifdef CONFIG_HAVE_ARM_SCU
 unsigned int scu_get_core_count(void __iomem *);
 int scu_power_mode(void __iomem *, unsigned int);
+#else
+static inline unsigned int scu_get_core_count(void __iomem *scu_base)
+{
+	return 0;
+}
+static inline int scu_power_mode(void __iomem *scu_base, unsigned int mode)
+{
+	return -EINVAL;
+}
+#endif
 
-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) && defined(CONFIG_HAVE_ARM_SCU)
 void scu_enable(void __iomem *scu_base);
 #else
 static inline void scu_enable(void __iomem *scu_base) {}